I had 8 users displayed in WPforo Members.
I had 8 members in WP Users and deleted 3 test users.
When wanting to sign in again with an earlier used Username/mail address I was advised in the front end that this user already exists.
I noticed in "WPforo members" those users deleted before in "WPadmin - Users" were still there and when trying to deleted the users got this message:"User deletion is not allowed from this screen".
What can I do to fix this? (I run a WP multi site installation)
Hi Sofy, I am looged in as Super Admin. - So it appears to be a bug.
Where in the db can I manually remove them please?
As I've already mentioned, user deletion is managed by WordPress, so you should find the issue outside of the wpForo plugin.
Where in the db can I manually remove them please?
To manually remove users from the database, you can follow the instructions in this article: https://www.stevesims.com/how-to-delete-a-wordpress-user-in-phpmyadmin/