Have only had one issue (within weeks of the +membership coming out) and it was because they didn't know I could be on an Alaska flight too and not just an AA flight to access. Was resolved quickly and that was EWR, (which is probably one of their worst lounges at a major airport). I have since used EWR and many others and like all the other responses have had no issues. Pretty simple too. Show your boarding pass (AA or Alaska for domestic), then you show them you Alaska + membership card in you digital wallet and all good.