No, I did not set a passphrase... but at this point, yea, I have contacted Trezor support and hopefully they can manage to find a solution.
As far as I can tell... the "pairing" is dependent on the hardware wallet having the same "xpub" as what was used to create the wallet. I do not believe that it uses any other identifying features such as the device name or device ID number.
Theoretically, the only way for the xpub to change would be for the underlying seed to have changed...
You already tried "restoring" the wallet by recreating the MultiSig using the original co-signer xpub + your hardware wallet didn't you?