Hello, and sorry if my question seems silly (I'm new to FlyerTalk).

I'm a United Airlines Gold member, which should give me a free checked bag if I'm flying on LOT, regardless of the fare class I booked. However when I try to input my UA MP number in the booking system, I keep getting an error message saying the format is not accepted (it only accepts numbers). This seems strange because my UA MP number in the format of 3 letters + 5 numbers.

Has anyone else had this problem?

In the worst case scenario, if the system doesn't accept my UA MP number, is there another way I can get the free checked bag? Can I just show up at the airport and show them my Star Alliance gold card to get the free bag?

Thanks!