Agree that there is an issue between AC and UA. UA does not recognize my frequent flyer number as valid either - says that either the name or number is incorrect. UA keeps insisting it is AC's problem, but I bought the ticket from UA, flying on UA metal. It probably has to do with my last name which is hyphenated and somewhere UA isn't recognizing it. I gave up and filed a claim with AC later. I was able to show my *Gold status to access the lounge and to board in Zone 2, but I suspect this would be a bigger problem if I had to check bags.