Please ensure everything installed is completely up to date. You can do this quickly from within CB > Plugin Management > Install New Plugin > Install from Web then selecting the Updates category. Once done navigate to CB > Tools and run User Synchronization. Be sure to only create users from CB > User Management if doing so from backend or through CBs registration page if doing so from frontend.

My guess is you may have an invalid activity entry from something. If this was previously working fine see what activity was recently logged and try unpublishing it. As a quick test you can change the Asset for the Activity tab in CB > Tab Management to something like "TESTING" then see if issue persists. If issue goes away it's for sure caused by a profile activity entry.

Aside from that ensure both debug mode and maximum error reporting are enabled in Joomla global configuration then retry to see if it provides more details about the error. As is no location was provided with the error so I've no clue where in the code it's happening for you. If the location still isn't output try checking server error log at time of error to see if more details can be found there.

Please PM backend super administrator login credentials and will take a look. I don't see any issues in the code it self.