Originally Posted by
TomMM
Here is what I've noticed, if I get "This is not a Boarding Pass" and there is not a specific explanation as to why, it's SSSS. If it is for another reason such as validation of travel docs, there will be a message indicating the reason.
No rhyme or reason...both my wife and I had flown TATL in July so our passports had been recently used...we went to check in for Paris last week, and she got "this is not a boarding pass." So I fired up my trusty UA app on my iPhone, ran through check-in again, and got the option to take a picture of her passport. A minute later, we're both checked in and TSA-Pre.