I've been living in Germany for a few years as a permanent resident. Up to now I never bothered to get a German driver's license despite having one from Canada. I recently decided to finally to do it but realized that my Canadian license has been expired for a few months. Very stupid, I know. I am kicking myself for my inaction.
Am I out of luck and have to do the full process for getting a new driver's license? It's hard to find info on this specific situation and also difficult to contact the Führerscheinstelle due to COVID.
Being an American in Germany, I have dealt directly with this issue:
The All About Berlin link posted by @mark-johnson is consistent with my understanding, having asked around at a few driving schools when I first moved two years ago.
Your non-EU/EEA driving license is not valid after six months if you are a permanent or long-term resident of Germany. I am told that one may apply for exception for one year of validity in the event of a (documented) planned stay of no more than one year in Germany. See also the BMVI for the official FAQ. All told, it sounds like you have no immediate option to drive legally in Germany and haven't been doing so for quite some time.
Should you renew your Canadian license, definitely get documentation (preferably some official-looking piece of paper maybe even with a raised seal since Germans just love those) documenting when your license was originally issued - it has to predate when you moved to Germany (as officially on your Anmeldung). The problem of license tourism (also mentioned on the BMVI FAQ) is a squishy issue, but your local Beamter at the Führerscheinstelle may want you to prove that you didn't pop over to Canada to avoid getting a proper German license and all that entails since as a German resident, if you do not already have a license, you are required to go through the German process.
The same thing happened to my daughter - she obtained the US license, but could not get the German one within the 6 months, as she was under 17. So she had to do the whole thing again, with a little less practical hours in the driving school.