If you upgraded your tx, then problems started,
It's safe to say,
Your Tx has become the problem!
So I'd start there!
I had a similar experience,
Bought used P3p with no Tx, so bought a " A " Tx ( gl300a I believe )
I could get camera to move, with dial wheel, and yaw movements, but nothing else, showed Tx as being linked to the AC ( bird ), light was green on Tx! I thought WTH?
So after a week and a half with no answers, and no joy, I started playing with firmwares, on my 3rd attempt ( SUCESS )
I'll try to post my firmware versions when I get home, cannot remember ( tx was like 1.7.1 and bird was like 1.8.0 or something like that, pre encryption I believe! ) but I'll post correct pairing tonight ( if standard is the same with firmwares? I've never owned or even fooled with the standard, or 4K crafts, only pro and advanced! Maybe the standard GURUS can fill us in!
J Dot