At my local supermarket debit was down but credit card (Visa) was working.

That would make sense, since only Interac relies on Rogers, and it processes debit cards, not credit cards.

Could be one of two things:

1) the site has connectivity so only Interac is down

2) the site has no connectivity and can process credit transactions offline and queue them (don’t tell anyone their expired card will work), but not for debit.

> don’t tell anyone their expired card will work

The expiration date is stored on the card, so expired cards wouldn't work. Revoked cards (eg. ones replaced by the bank) would, though.

Keep in mind that the merchant sets terminal limits for what transactions are allowed to be processed offline, so one might be able to get a burger without connectivity, but not a new TV.