problem with the forum
Please remove the reCAPTCHA, wpForo doesn't support it with regular registration form. This is not wpForo issue, this is reCAPTCHA compatibility issue. if you want to use this, you should chage wpForo Registration mode to Email Confirmation way. Navigate to Forums > Settings > Features admin page and turn this option on:
still not working
I did it and it just does not work ..
If it doesn't work, then remove this plugin please, this is not compatible with wpForo. Try other reCAPTCHA plugins, there are dozens of them. Or ask this plugin developers to make it compatible with wpForo.
There saterproof reset all the settings of the plugin?