Long story short, I have a TP-issued ticket purchased from an OTA with the routing LIS-SFO-YVR, with LIS-SFO as a TP flight number on TP metal and SFO-YVR as a TP flight number and AC metal. It seems what has happened is that AC has dropped the TP codeshare, so the AC flight is still valid but the TP codeshare is not, so AC says I don't have a valid ticket for SFO-YVR. TP won't do anything and tells me anything has to be done through the OTA, AC won't touch it because it's a TP issued ticket, and the OTA insists that "TPXXXX is on-time" and therefore refused to take any action. What in practice will happen when I show up to the airport? I guess best case I fly to SFO and go to the AC counter, who would presumably have control of the ticket at that point and could re-issue it properly and allow me to fly. Or would I just be SOL with no way to get to YVR if the OTA won't acknowledge that the TP codeshare isn't valid anymore and AC won't accept a ticket for it as valid for travel? Or would TP possibly be able to fix it in LIS....I could also go to their ticket office at Lisbon Airport at T-24.

Wondering if anyone has any experiences with dealing with AC at the airport with an OTA ticket....will they fix it since they have control of the ticket by that point, or will they just tell me to call to OTA who won't help?