Technically, the system needs 2 or 3 keys to work properly, the 2FA supports a maximum of 100, and each time you set the 2FA, you create a new key.
There is an error showing that you have too many keys set on the account, this error while setting the 2FA will not allow you to proceed :
The only solution NEAR Wallet can recommend in this situation is to create a new account, transfer your assets there, and set the 2FA.
We understand that it may be inconvenient for our customers. We are working on improvements of key management in the NEAR wallet, so this error won't disturb you in the future.