[@robin-w Moderator 8 years, 11 months ago]

most likely your theme or another plugin is expecting bbpress to be there.

Plugins

Deactivate all but bbpress and see if this fixes. if it does, re-enable one at a time to see which is causing the error.

Themes

If plugins don’t pinpoint the problem, as a test switch to a default theme such as twentyfifteen, and see if this fixes.