The ubiquiti controller software listens to the Unifi broadcast traffic , however if this is on a different subnet you won’t get this!

To get around this , you need to create some records for the Access point to manually point to the controller

DNS

Create a DNS pointer of UniFi.domain.local on your DNS to point to the CNAME of your Ubiquiti Controller

DHCP

You can also use DHCP Option 43

        option ubnt.unifi-address 201.10.7.31;  ### UniFi Controller IP ###