Had this problem yesterday. Flew YYC-YYZ-CDG-YYZ-YYC. Obtained *A gold status on the outbound flight on November 24 and saw that my card was upgraded to gold Nov 29. Printed a screen shot of my account showing gold and the transactions to prove that it just happened. When I checked in yesterday in CDG to come home, AC didn't have my as gold, only silver. After checking in, I had to go to the AC ticket desk to get the change. Showed my screen shots and they changed my boarding pass after requesting it so that I could have priority boarding and lounge access without problems. She called down to the AC lounge to get me in and in our stopover in YYZ, no one asked for the card, just the boarding pass. The ticketing person could see in the system I was gold, but she had to do some digging. The paper print outs really helped.