I finally got Captcha to work on all of my sites. I found the problem.
I had an empty enter, new line or space at the end of my english.php located in includes/languages/YOUR_TEMPLATE/english.php

This must have happened when I edited some lines for the footer customization. Hard to see with the editor. I just hit delete a few times at the end of the file and made sure no extra space or anything remains. If you have the same problem that there is no captcha, just the "Enable this picture" text, check out your english.php in your template override folder. Last thing in the file has to be just ?>

Don't know why this affected Captcha only but not the other customizations in the english file. All other customized text in the file worked just fine.