Sessions are empty. What do I need to turn on?

Accounting is set up separately from authentication, so a network that authenticates fine can still send Passbeam nothing about sessions. You need two things.

Add Passbeam as an accounting server on port 1813 in the same RADIUS profile you already use for us. Add both addresses, the same as for authentication, with the same shared secret. In UniFi it's the Accounting Servers box under the authentication servers. If there's an update interval, set it to 300 seconds.

Allow UDP *and* TCP 1813 outbound on the firewall. That's two rules. A rule for only one protocol looks right and lets nothing through. It's the most common cause, because the equipment tries, gets no answer and gives up without showing an error.

After that, a session appears the next time a device connects. Devices already connected may not show until they reconnect, because the equipment only reports sessions as they start.

If it's still empty, check the authentication log. If devices aren't authenticating either, the problem isn't accounting.