I have a LH FRA-TXL flight that did not credit automatically. Online retroactive credit also does not work. The system tells me "A mileage credit was not possible". This leg was part of a TXL-FRA-SFO-FRA-TXL itinerary booked in PE and upgraded to Business. I suspect the problem is that on the return flight the upgrade only cleared for the SFO-FRA part, and not for FRA-TXL. I then inquired in FRA and they then manually gave me an upgraded boarding pass for FRA-TXL (showed I class).

What is the best way to get credit for this flight? Not clear from web site what to do if online tool does not work.