It shouldn't be a problem with all the proof you have.
I guess they are re-assessing some past "unpaid damage charges or claims" and decided to chase for it now.

No business travel, no international travelers, provincial lockdowns, US/Canada land border conditional closure
Most Canadian rental locations do not have the shortage problem and price is still reasonable.
Therefore, they may try to find other ways to earn some extra cash.
They already told me no charges 5 months ago and now this.