Problem

An A/P CFT is registered into CG

No cluster IP (DNS) is defined

No Load-balancer is set

After a fail-over, CFT is not seen active from CG

Resolution

For any A/P installation you need a load balancer or a DNS mechanism.

Only such a mechanism allows a remote peer to connect to the A/P CFT instance disregards the host where CFT is running.

The remote peer knows only the load balancer address or a DNS address.

It is exactly the same for CG, considering that CG is the remote peer.

So you must implement an LB or a DNS and, you set the uconf:cft.full_hostname parameter to the address of the LB or the DNS prior to register CFT to CG.

Since you are in A/P mode, only the active one perform the registration. It registers the entire instance.