If you are locked out of your Canada Revenue Agency (CRA) My Account, then you will not be able to use Auto-Fill. You will need to either contact the CRA to get your account unlocked or enter your slips in manually.
If you are in Canada or the United States, you can call the CRA at 1-800-959-8281. If you are elsewhere, you can call 613-940-8495. This page has more ways to contact the CRA: Contact the Canada Revenue Agency