Wondering if I can get some thoughts from others, to see if my anger is valid or misguided.

Partner and I were travelling from LHR back to Canada, on AC. Booked on the same ticket, partner is 50K and I have no status. We'd checked in on the AC app in advance.

We were running late. Bag drop deadline is 8am at LHR. We ran and got to the AC priority checkin desk at 7:57am. That was when we handed our passports to the agent, as I looked at the screen above the agent to confirm we still had time. I actually high-fived my partner, because we'd made it (which if you were watching this as a movie, would have been ominous foreshadowing).

Agent is tapping away and saying nothing, and partner and I were chatting. She then says to us, "sorry, you're late, I cannot checkin your bags". I look up and the sign above her now says 8:01am. We both stared at her and said, but we weren't late when we arrived. She then tells us we needed at least 10 more minutes to drop our bags. We ask is there anything she, or the other (SE checkin) agent can do, like opening the flight to allow the bags to be checked? They both say no, we need to go to ticketing to get them to re-open the flight. Partner has been SE in the past and had them reopen a flight when hes arrived late, so we were pretty sure it could be done.

We run to ticketing. Get there at 8:03am. That person flat out refuses to try or do anything. Says there are no other flights available today. Says we're now considered to have missed the flight, we need to re-book and pay for a new flight, and because this was an aeroplan ticket, we need to call aeroplan ourselves to rebook.

We were kind of in shock at this point. Panic then ensued, including attempts to ship luggage and send it back to our friends. Ultimately decided that I would run to the gate with no checked bags, as I needed to be home for work. I hustled and arrived at the gate at 8:39/8:40am (again, looking at the screen above). Gate cutoff is 8:45, boarding was to start at 8:25. Doors are closed, everyone is onboard, and they proceed to tell me that I had been offloaded from the flight as I had missed it. Ended up getting rebooked with my partner for the next day.

Am I wrong to think that this should have been fine, and we shouldn't have had an issue, even though it was really close to the deadline? I've arrived before with minutes to spare, with AC (with and without AC status), and never had an issue like this happen before, with a kiosk or an agent, but maybe that was just luck? Should we have just gone to a kiosk and printed tags ourselves? Am I wrong to be angry that this happened?