According to the above reply from ircc seems you can still send in your passport with an expired letter if you've paid the 2 way fee and you Visa office is operational. Maybe you aren't going to get another one since it's been issued already, but should rather send your passport with your expired letter. The worst that could happen is that they send your passport back without issuing your visa? Idk Ijs...that's what I'd do.
"
Good day,,
Thank you for contacting Immigration, Refugees and Citizenship Canada (IRCC).
We have verified the information you provided. For further information regarding your enquiry, please refer to the email that was sent to you on February 27, 2020 to the following address:****
We recommend that you also verify your junk mail folder, since emails may be rerouted there if your email program is set to filter or block emails coming from outside of your contact list.
Furthermore, since this letter was sent by email, it will not be available in the messages section of your online account.
If you have not received our email, you may advise us by using the
IRCC Web form and it will be our pleasure to send it back to you."
I reached out to them several times via webforms and phone calls, so by now they know I didn't get my PPR.