This is a fairly common issue and most of the time, can be resolved fairly easily. Lots of software distributors use Captcha systems in order to try and block pesty spam bots. You may find that your Captcha images are not loading and may just show a broken link or something similar. If this is the case, you're most likely missing the PHP module, GD. Learn more about GD: http://php.net/manual/en/book.image.php
If you're using cPanel on your server, installing GD is a piece of cake and can be installed with just a couple of clicks. Firstly, it's best to verify that GD is indeed not loaded on your server. If it is loaded, then you will need to look further into the issue.
To check if GD is enabled or not, simply run the below command:
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php -m | grep gd
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If you have GD enabled, you will see an output like the below:
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root@server [~]# php -m | grep gd
gd
root@server[~]#
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If GD is not enabled, you will be returned with a blank prompt which will look like the below:
root@server [~]# php -m | grep gd
root@server[~]#
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So, how do I load/install GD into my PHP configuration with cPanel?
Good question, here's how:
1) Login to WHM (yourserverip:2086) with your root credentials.
2) Click on EasyApache (Apache Update) located under Software.
3) Click on Start customizing based on profile.
4) Click Next Step - you should be on the Apache Version section.
5) Click Next Step - you should be on the PHP Version section.
6) Click the blue Exhaustive Options List button.
7) Search for GD on this page and tick the check box.
8) Scroll down and select Save and Build.
I've built Apache with GD and that didn't fix my issue, now what?
Your script may be using another PHP module, known as TTF (FreeType) and so if the above steps didn't work, we recommend following them again and this time ticking the box with TTF (FreeType). You will now have both GD and TTF loaded on your server and should your issue still not be resolved, we recommend opening a support ticket with us if you're a Managed client. Alternatively, you can contact the developer of your script and ask for their advice.