It wasn’t a question of being vaccinated, everyone had to produce a negative test, and again on arrival. I understand a change july 5, Canadá is only accepting certificate I believe from 4 of the vaccines. Best to check the Canadá website,
As u say, things change daily. My friend needed the tests to re enter New Zealand. (September) I just returned from the US , to be allowed on the plane it was necessary to produce a negative test (within 72 hours) going and returning.
I understand that if YOU cancel there is only a credit. If the airlines cancel they will offer you a 2 year credit, if you accept this, there is nothing more, if you say No, then they need to refund your money.