Need to remember, UA does not process the upgrade for ANA flights. Using the electronic interface, a request is forward to ANA to request ANA to process the upgrade. No UA agent can do anything. And generally will have no knowledge about how it works since they are never involved.

That electronic interface to ANA goes to thru the *A system and occasionally breaks. Again other than to report the issue, no UA agent can process the upgrade. To complete the upgrade ANA needs to request "payment" for upgrade per agreement with UA and UA will debit your account for the PlusPoints