Problem pairing Garrett z-lynk

Got a new pair of MS-3 headphones to replace the MS-2 for my AT Pro but the MS-3 won't pair with the exisiting transmitter 1 on the Pro. The transmitter pairs with the receiver for the MS-2 phones fine. I got it to pair once initially but not now. Any idea what's up? Was thinking that maybe there's some sort of frequency difference but I don't think that's the case. Maybe it's just bad from the get go. Any thoughts appreciated.