a PR card expires after 5 years but PR never expires so are you saying you failed to meet the residency requirement ? If so maybe look in the residency obligation thread for tips how to reenter Canada given as still being PR you would still be allowed into Canada but there is a risk of being reported for not meeting RO.
First challenge may be that you need a PRTD to travel back to Canada without a current PR card but look in the RO thread for more examples.