Thank you both, Polar Man and cecric.
Yes, I filed my claim under APPR.

I received an answer one month later FROM WEST JET that they understand I ffiled my claim, and said:

Upon review of your reservation, we are unable to approve your claim for compensation as the most significant reason for your flight disruption was due to regulated crew rest or crew availability impacted by factors outside the airline's control and or an inability to schedule another operating crew due to the flight departing from an airport with no crew base and was required for safety purposes.

I really thought when I file a claim with APPR, I receive an answer from APPR, but no: I received the answer from WEST JET.
The same was happening with DOT another month later. Again, an answer received from West Jet, declining their responsibility.

No answer from CTA yet.

There does not seem to be any way at this time to dispute the reason for West Jet canceling their flight.
West Jets claims it is crew availability while our captain said it was the number of passengers not aligning with the manifest.

I wish I was recording his announcement when it happened...!
(But then nobody would listen to the recording anyway - all that matters seems to be the reason that WEST JET files in the official records.)