Have never had it happen, but I have been using mypost business since it started, twice auto tracking update to ebay order has failed.  Both times I have been advised of the failure by AP, and on both occassions was able to then perform a manual update  as tracking details are still available in AP.    Out of habit, I still keep the paper lodgement receipt, as at one stage it was the only proof PP would accept.

Just wondering if by some chance the numbers and carrier you upload are incorrectly cross referenced  against the incorrect buyer/item.  Or simply entered details are incorrect,   I do recall once I manually entered a wrong  tracking number, and was advised a couple of days later from buyer that the tracking was incorrect,

apparently I had inadvertently transplaced 2 digits