Had a 2.5.8 site where the integrated Capcha stopped working. Tried some things that others suggested, but nothing worked.

  1. Changed a line of code in the Recapcha php file as suggested in the Joomla Forum. Didn’t do anything.
  2. Regenerated new keys. Didn’t do a thing.

I got it fixed by updated my Joomla core install from 2.5.8 to 2.5.11 and the capcha was working again.