Found the answer, its a bit silly but if anyone else gets the same issue…
After you add a new user to the “Testers” he gets a notification that he must accept, so the “Pending” will go away, and the user will be activated.
This notification does not get to the Facebook home page, only to the “Developer section” of that user. As @rmp251 mentioned, that can be found on this page
Thanks for the help.