Calls from PSTN to Grandstream GXW4104 end with dial tone

Configuring a Grandstream GXW4104 PSTN Gateway with FreePBX and AT&T analog trunks.
All is working except for inbound calls. They don’t come into my inbound route but end with dial tone.
I guess it’s a misconfiguration on the Grandstream, that it’s not forwarding the traffic to the PBX properly.

Anybody familiar with these devices?
I largely followed this guide: