Originally Posted by renegurl

I have a similar story too. I booked AA codeshare flights through Citi Thankyou. (For some reason, CX was showing Y and PEY was sold out, but AA still showed availability.) I've booked AA codeshares before on AA.com and the drill is to ask AA for the CX record locator and then I would be able to pull up my booking on the CX website and manage my seat.

The website has an error if I use my name/record locator. I appended my middle initial as usual and that didn't help. When I look it up with my ticket number, it says "No RLOC Associated with this ET". If I pull it up on the CX app, I can see the itinerary but I can't make any edits like seat selection. It just says refer to the operating carrier. The booking ref also works in checkmytrip - which lets me see the seat map.