Capatcha image not displayed but error message

I have got NatSkin installed with all dependencies I even tried to reinstall CaptchaPlugin with the $ perl tools/extension_installer CaptchaPlugin install . In /System/UserRegistration form there isn't a captcha picture displayed but rather a large pop-up error message jumps in front.

After closing the error message and while clicking on [Get a different image], the error message re-appears.

What can cause the issue?

Error: Can't locate GD.pm in @INC (you may need to install the GD module) (@INC contains: /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib . /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.30.0 /usr/local/share/perl/5.30.0 /usr/lib/x86_64-linux-gnu/perl5/5.30 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.30 /usr/share/perl/5.30 /usr/local/lib/site_perl /usr/lib/x86_64-linux-gnu/perl-base /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/CPAN/lib) at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage/GD.pm line 36.
 at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage/GD.pm line 36.
    GD::SecurityImage::GD::BEGIN() called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage/GD.pm line 36
    eval {...} called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage/GD.pm line 36
    require GD/SecurityImage/GD.pm called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage.pm line 42
    GD::SecurityImage::import("GD::SecurityImage") called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Plugins/CaptchaPlugin/Captcha.pm line 29
    Foswiki::Plugins::CaptchaPlugin::Captcha::BEGIN() called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage/GD.pm line 36
    eval {...} called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage/GD.pm line 36
    require Foswiki/Plugins/CaptchaPlugin/Captcha.pm called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Plugins/CaptchaPlugin/Core.pm line 102
    Foswiki::Plugins::CaptchaPlugin::Core::jsonRpcCreate(Foswiki::Plugins::CaptchaPlugin::Core=HASH(0x55f3beb034d0), Foswiki::Contrib::JsonRpcContrib::Request=HASH(0x55f3beafb490), Foswiki::Response=HASH(0x55f3bd4a4a20), undef) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Plugins/CaptchaPlugin.pm line 72
    Foswiki::Plugins::CaptchaPlugin::__ANON__(Foswiki=HASH(0x55f3bd4a4918), Foswiki::Contrib::JsonRpcContrib::Request=HASH(0x55f3beafb490), Foswiki::Response=HASH(0x55f3bd4a4a20), undef) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Contrib/JsonRpcContrib/Server.pm line 172
    Foswiki::Contrib::JsonRpcContrib::Server::__ANON__() called at /usr/share/perl5/Error.pm line 465
    eval {...} called at /usr/share/perl5/Error.pm line 454
    Error::subs::try(CODE(0x55f3beaf5958), HASH(0x55f3beb035d8)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Contrib/JsonRpcContrib/Server.pm line 184
    Foswiki::Contrib::JsonRpcContrib::Server::dispatch(Foswiki::Contrib::JsonRpcContrib::Server=HASH(0x55f3be715208), Foswiki=HASH(0x55f3bd4a4918)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Contrib/JsonRpcContrib.pm line 35
    Foswiki::Contrib::JsonRpcContrib::dispatch(Foswiki=HASH(0x55f3bd4a4918)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/UI.pm line 374
    Foswiki::UI::__ANON__() called at /usr/share/perl5/Error.pm line 465
    eval {...} called at /usr/share/perl5/Error.pm line 454
    Error::subs::try(CODE(0x55f3bc1dc5c0), HASH(0x55f3bd4a4348)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/UI.pm line 500
    Foswiki::UI::_execute(Foswiki::Request=HASH(0x55f3bcc68428), CODE(0x55f3bcd09980), "jsonrpc", 1) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/UI.pm line 326
    Foswiki::UI::handleRequest(Foswiki::Request=HASH(0x55f3bcc68428)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Engine/CGI.pm line 100
    Foswiki::Engine::CGI::run(Foswiki::Engine::CGI=HASH(0x55f3bcd117b8)) called at jsonrpc line 31
BEGIN failed--compilation aborted at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage/GD.pm line 36.
 at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage/GD.pm line 36.
    require GD/SecurityImage/GD.pm called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage.pm line 42
    GD::SecurityImage::import("GD::SecurityImage") called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Plugins/CaptchaPlugin/Captcha.pm line 29
    Foswiki::Plugins::CaptchaPlugin::Captcha::BEGIN() called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage/GD.pm line 36
    eval {...} called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage/GD.pm line 36
    require Foswiki/Plugins/CaptchaPlugin/Captcha.pm called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Plugins/CaptchaPlugin/Core.pm line 102
    Foswiki::Plugins::CaptchaPlugin::Core::jsonRpcCreate(Foswiki::Plugins::CaptchaPlugin::Core=HASH(0x55f3beb034d0), Foswiki::Contrib::JsonRpcContrib::Request=HASH(0x55f3beafb490), Foswiki::Response=HASH(0x55f3bd4a4a20), undef) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Plugins/CaptchaPlugin.pm line 72
    Foswiki::Plugins::CaptchaPlugin::__ANON__(Foswiki=HASH(0x55f3bd4a4918), Foswiki::Contrib::JsonRpcContrib::Request=HASH(0x55f3beafb490), Foswiki::Response=HASH(0x55f3bd4a4a20), undef) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Contrib/JsonRpcContrib/Server.pm line 172
    Foswiki::Contrib::JsonRpcContrib::Server::__ANON__() called at /usr/share/perl5/Error.pm line 465
    eval {...} called at /usr/share/perl5/Error.pm line 454
    Error::subs::try(CODE(0x55f3beaf5958), HASH(0x55f3beb035d8)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Contrib/JsonRpcContrib/Server.pm line 184
    Foswiki::Contrib::JsonRpcContrib::Server::dispatch(Foswiki::Contrib::JsonRpcContrib::Server=HASH(0x55f3be715208), Foswiki=HASH(0x55f3bd4a4918)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Contrib/JsonRpcContrib.pm line 35
    Foswiki::Contrib::JsonRpcContrib::dispatch(Foswiki=HASH(0x55f3bd4a4918)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/UI.pm line 374
    Foswiki::UI::__ANON__() called at /usr/share/perl5/Error.pm line 465
    eval {...} called at /usr/share/perl5/Error.pm line 454
    Error::subs::try(CODE(0x55f3bc1dc5c0), HASH(0x55f3bd4a4348)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/UI.pm line 500
    Foswiki::UI::_execute(Foswiki::Request=HASH(0x55f3bcc68428), CODE(0x55f3bcd09980), "jsonrpc", 1) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/UI.pm line 326
    Foswiki::UI::handleRequest(Foswiki::Request=HASH(0x55f3bcc68428)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Engine/CGI.pm line 100
    Foswiki::Engine::CGI::run(Foswiki::Engine::CGI=HASH(0x55f3bcd117b8)) called at jsonrpc line 31
Compilation failed in require at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage.pm line 42.
 at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/GD/SecurityImage.pm line 42.
    GD::SecurityImage::import("GD::SecurityImage") called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Plugins/CaptchaPlugin/Captcha.pm line 29
    Foswiki::Plugins::CaptchaPlugin::Captcha::BEGIN() called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Plugins/CaptchaPlugin/Captcha.pm line 29
    eval {...} called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Plugins/CaptchaPlugin/Captcha.pm line 29
    require Foswiki/Plugins/CaptchaPlugin/Captcha.pm called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Plugins/CaptchaPlugin/Core.pm line 102
    Foswiki::Plugins::CaptchaPlugin::Core::jsonRpcCreate(Foswiki::Plugins::CaptchaPlugin::Core=HASH(0x55f3beb034d0), Foswiki::Contrib::JsonRpcContrib::Request=HASH(0x55f3beafb490), Foswiki::Response=HASH(0x55f3bd4a4a20), undef) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Plugins/CaptchaPlugin.pm line 72
    Foswiki::Plugins::CaptchaPlugin::__ANON__(Foswiki=HASH(0x55f3bd4a4918), Foswiki::Contrib::JsonRpcContrib::Request=HASH(0x55f3beafb490), Foswiki::Response=HASH(0x55f3bd4a4a20), undef) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Contrib/JsonRpcContrib/Server.pm line 172
    Foswiki::Contrib::JsonRpcContrib::Server::__ANON__() called at /usr/share/perl5/Error.pm line 465
    eval {...} called at /usr/share/perl5/Error.pm line 454
    Error::subs::try(CODE(0x55f3beaf5958), HASH(0x55f3beb035d8)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Contrib/JsonRpcContrib/Server.pm line 184
    Foswiki::Contrib::JsonRpcContrib::Server::dispatch(Foswiki::Contrib::JsonRpcContrib::Server=HASH(0x55f3be715208), Foswiki=HASH(0x55f3bd4a4918)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/Contrib/JsonRpcContrib.pm line 35
    Foswiki::Contrib::JsonRpcContrib::dispatch(Foswiki=HASH(0x55f3bd4a4918)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/UI.pm line 374
    Foswiki::UI::__ANON__() called at /usr/share/perl5/Error.pm line 465
    eval {...} called at /usr/share/perl5/Error.pm line 454
    Error::subs::try(CODE(0x55f3bc1dc5c0), HASH(0x55f3bd4a4348)) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/UI.pm line 500
    Foswiki::UI::_execute(Foswiki::Request=HASH(0x55f3bcc68428), CODE(0x55f3bcd09980), "jsonrpc", 1) called at /home/wsgadmin/domains/wsgtest.domain.eu/public_html/foswiki/lib/Foswiki/UI.pm line 326
    Foswiki::UI::handleRequest(Foswiki::Request=HASH(0x55f3bcc68428)) called at /home/wsgadmin/domains/wsgtest.domain.eu

-- CieskaIzabelijus - 21 Feb 2021

Right at the beginning of this long series of error messages, you'll find the source of your problems. As it says, it can't find GD.pm, which is the CPAN:GD modules that is a dependency for CaptchaPlugin. Foswiki's plugin installer can not install these external perl modules (as it states at the end of the install process) so you must do that separately, depending on your particularly server environment.

-- LynnwoodBrown - 22 Feb 2021