Getting ready for a trip to Milan and went to the Travel Ready Center. United said I had no passport on file despite uploading one for a trip a couple of weeks ago. So, I decided to upload a new one.
My first webcam photo went through a lengthy "verification" process which completed successfully, but before leaving I noticed the last digit of my passport was missing. Went back, took a new webcam photo, waited for the long verification. This completed successfully, except that now my U.S. passport verified as being from Mauritius. Next, I tried a high res scan from a flatbed scanner - properly aligned, crystal clear... verified that the stated nationality of the passport was United States prior to the scan... and it came back as Mauritius again.

I guess I can just show my passport at the airport, but is there a workaround for this? And how are these "verifying" with incorrect info (e.g., last digit missing)?

UPDATE: I decided to try from my phone (Galaxy S21U). Took a photo, and the United app (normally very reliable) crashed while "reading photo." Tried again, same result. Did a hard reboot on the phone, and this time the scan worked - back in the USA! Very odd experience overall, how on earth do you take a high res scan of a US passport and verify it's valid from Mauritius??

UPDATE #2: Having completed the pre-flight docs for the outbound trip, I thought I might as well be sure my info for the return leg a week later was good to go. First thing I get is, "You have no passport on file," even though I had just successfully uploaded one for the first trip. Looks like just another example of the dumpster fire that is United IT.