I don’t know if it’s still the case, but In the past at least, a POUG used to make a flight completely non changeable (you couldn’t even if you were ok losing the upgrade) I wonder if this is the problem here. From what you describe, the first upgrade some months ago did not cause a problem, but if it was not a promotional upgrade but a fare difference upgrade it would have been ok.i know the second has roughly the same price. Are you trying to change into W or into J?