Did you try disconnecting/unplugging the hardware wallet... and then shutting down Electrum (and/or even restarting the computer completely)... and then try repairing your Trezor with the multisig wallet?

I've had issues in the past with Electrum when trying to switch from one hardware wallet to another hardware wallet without disconnecting the device... where the device won't be "detected" after trying to switch wallets until I shut everything down and then start again.