Did you try some troubleshooting to see if it could be a possible theme issue. Some theme frameworks do not play nice with bbPress’s theme compatibility, so try to check in a default theme to see if it works fine.
Troubleshooting
I guess you can also ask these questions too.
Did you import any users?
Are you allowing users to register with their email?
I really appreciate your suggestions on this issue…
Mine was a theme problem… Twenty Fifteen restored normal functionality.
Thanks so much.