By "Legacy Account" they're probably referring to this
Yes. It should be as simple as hooking up the correct Trezor device which recovered the segwit wallet, and using either the Trezor software to re-add the legacy account or using Electrum to open a new wallet using P2PKH at m/44'/0'/0'.
It sounds like OP is trying to restore from a seed phrase which is the wrong seed phrase for the Trezor in question.