You can file without your Netfile Access Code. It is not mandatory.
If you are locked out of NETFILE, you will need to contact the CRA and get unlocked. 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
Your NETFILE account is not the same as your CRA MyAccount. You don't need MyAccount to use NETFILE.