Also was having this error. Had a multisig and 2FA wallet.

This worked for me:

1. Sent my BTC to a different wallet.
2. With Electron Cash (version 2.9.2):
2.1 Entered a new name to create a new wallet.
2.2 Choose "Standard wallet".
2.3 Choose "I already have a seed".
2.4 Entered seed of my original (BTC) wallet.
2.5 Choose "Disable" (2FA).
2.6 Sent BCC to bittrex BCC address