Captcha does not save form_id I added the CAPTCHA module to my drupal 6 website using this procedure and I'm trying to add the captcha to my user registration page.

However when I go to /admin/user/captcha the list with the default forms is empty. I expected the default list.

I entered user_register as the form_id, selected the standard captcha from the dropdown and pressed save. However it does not add the new form to the list. It's still empty. I also tried to save other values without success.

UPDATE:
I also tried reinstalling the captcha module and flushing cache without success. It's weird because I never had this problem on an other site with the same module/version

Installed version of the module: 6.x-2.4

UPDATE 2:
I enabled both the Captcha module and the Captcha compatibility module in the modules list.
The problem was the site didn't have writing permissions to the database. This meant that on installation of the module the necessary tables where not created and thus the above problem occurred.