Not able to add payee for an expense

I had a member bring me a receipt to be reimbursed for a ward expense, but it doesn't show them in the list of payee's. I tried to add them to the list of payee's with their MRN, but it gave me the error "Invalid MRN", even though I copied it from the Members List. Not sure what to do, any help would be great.

That indicates to me that the person is an adult (18 years old or older) who was a child of record (had a membership record) but has not been baptized. Check their record in the ordinances section for both a baptism and confirmation. They most likely do not have one or both recorded.

They can be added as a nonmember payee.

Edit: I would also assume anyone 9 years old or older that is not baptized would not appear on the payee list as described above.