Did you reconfigure your SCCM out-of-band settings to point to ServerA as instead of Server1? If you use the WS-MAN translator, you will need to update the setting in there as well. Finally, you will want to make sure that you have the updated and full cert chain for your new CA environment in your SCCM server's computer account trusted root cert store.
Can you send the amtopmgr.log in order that I can see what's going on?
Have you restarted the SMS Execute after you changed the CA appointment? As far you changed the server, did you granted SCCM computer account permission on new server template?
Possibles causes on top of my head.
My two cents!