If the offer link is still active, you may select it to accept. The university is allowing you to accept this offer after the expiry date. However, before accepting this offer, you should contact the university to verify how long the offer is valid after the expiry date, especially if you are cancelling an accepted offer to accept the expired offer.

If the offer link is not active, the university is not allowing you to accept this offer after the expiry date. If you still want to accept the offer, you will need to contact the university directly to see if they will send a new offer to the OUAC for you to accept.