Have you enrolled yourself in to the program and taking online classes right now? If yes, then your expired LOA can work BUT you will need enrolment confirmation letter from institute so that CBSA can verify both of these documents. If you haven't started your classes yet and LOA is expired then that may cause some headache at the border. According to following link under Documents required at port-of-entry, you need a valid LOA.
https://www.canada.ca/en/immigratio...-canada/study-permit/prepare-arrival.html#s01
Documents you need
When you meet the border services officer, you may have to show them:
- a valid passport or travel document
- the letter of introductionthe visa office sent you when they approved your study permit
- This letter has your permit reference number, which we use to issue your study permit
- a copy of a valid letter of acceptance from your school
- proof that you have enough money to support yourself during your stay in Canada
- letters of reference or any other documents the visa office told you to bring and
- either a valid Electronic Travel Authorization (eTA) or visitor visa (temporary resident visa)
- If you have a valid eTA, it’ll be linked to the passport you used to apply for your study permit