The Captcha image doesn't show
Please see this FAQ How do I add a Captcha to my form? to set up Captcha.
If the images do not display then there is probably a permissions problem and the server is not allowing the image to be created. Changing the 'Load Encoded Image' setting in the Load Captcha action to 'Yes' may resolve the problem.
If not, you can get more 'informative' error reports if you change the header at line 32 in the file components/com_chronoforms/chrono_verification.php from
Then point your browser directly to that file:
It will show PHP errors on things php cannot handle. This should provide enough input to fix any problem with the server settings..
Remember to change the header back afterwards.