Aria mobile check in

ok so I was trying todo the mobile check in for Aria. But it keeps popping up a message saying your reservation cannot be found. After calling the Aria and speaking to Ashley, she was able to go to the payment part of the mobile check in but cannot take a credit card over the phone as to she is only a concierge. She stated guest has problems using it all the time. now here's where I'm going here. If u offer mobile check in why can't your guest check in using it? MGM needs to steep up there game and roll out check in kiosk instead of paid parking.