Have had several POUG come up and have been taking them up, most of the time without problems.
Recently though I've had a few glitches both on the app and the site whereby I cannot complete the payment. Everything goes through fine after the Amex verification check (safe-site or whatever it's called), then the site returns an error saying the upgrade offer is no longer available for me. Very annoying given that it let's you go through with it right to the end (payment).
Also on the app when the POUG offer appears I get an error that my 'payment details cannot be loaded' and so I cannot complete the transaction. Generally I am able to do the POUG at online check-in without any issues.
Are these known issues or am I just really special?