I'm a U.S. citizen and a Canadian PR. For the past year I've been driving to upstate NY to help my brother take care of our 94 year old mom. My PR card expired this past May and I was delayed in submitting the renewal application due to Covid and not being able to have photos taken until recently. I drove back to Canada last Sunday with my expired card. There was no problem -- border guard just mentioned that I'll need to show the receipt for the PR renewal on any future crossings. Just posting this for anyone in a similar situation. (Doing my 14 day quarantine now.)