Provision second W52H to existing base and 3cx

I have a working W52P base and handset setup provisioned with a v12 3cx pbx. I can see the base / handset in the phones listing along with the MAC address of the base. Now, I pair a second handset to the base and can see the new handset in the yealink GUI. I have also created an extension in 3cx for this new handset, but I cannot select the actual phone because it will require a MAC address which does not exist for the handset itself. I have found if I setup a second account using the yealink GUI, I will then see the new extension as registered in 3cx, but not provisioned. Is this the expected status for a second handset or am I not setting it up wrong? I can only find documentation on the first handset / base combination.

Thanks,
Tim