Uh, why did they do this, you cannot run Unifi.app in /Applications, it needs a writeable directory. So it needs to live in a writeable place like /Applications/Unifi/Unifi.app and make /Applications/Unifi writeable, but this didn’t seem to help.
What did was to delete and reinstall and then it seemed to work after a reboot. I don’t know why.
The Unifi Discover application seems to take a long time.
This thing remembers old installations and removing the application doesn’t help, so if you have ever installed 3.x or 4.x, you will need to recover your password
If you have lost your password, you have to download Mongo, then run the bin/mongo, use ace and run db.admin.find() and you can see the password in clear text. Yikes, this is not the most secure system.