Access Points removed from Central after expiration of trial, cannot manage on local XG even after reset of APs

We had a series of APX320 Access Points registered on Central on a Wireless Trial.

The Customer decided not to use Central after all.

We then removed a few before the end of the Central Wireless Trial and connected them to an XG without problem.

The rest we did not remove immediately from central.

Some time later, after the expiration of the Central Wireless Trial, we removed the rest from central.

We are now trying to connect two of those to an XG.

The XG is the Default Gateway for the network and we have added the "234" DHCP option for good measure.

Yet even after doing a full reset of the Access Points they don't show on the XG.

A packet capture of the traffic from the Access Points shows a lot of traffic to what I suppose is Sophos Central.

The Access Points make no attempt to contact the IP 1.2.3.4 or the Gateway over Port 2712

How do we get Access Points connected to the XG?