Please ignore it. It seems you had spam users and some data are left in the database after deleting them. Please navigate to Dashboard > Forums > Settings > Features admin page and set "Yes" the "Turn Off User Syncing Note" option.

I have a strange warning that pops up on every page of the wordpress dashboard not just in wpforo's dashboard (see image attached).

It says that installation is at 100% but also that "Forum users' profile data are not synchronized yet, this step is required! Please click the button below to complete installation." 

This warning appears regardless of whether the synchronization in settings > features is set to Yes or No. 

When I click the button on the warning to "continue synchronization>>" nothing happens. 

I click "continue sync.." and then change the sync setting in features to enable it and still nothing happens. The warning remains. 

Why wont it go away? 

Please advise.