Best of luck finding anybody who can help nowadays - but you need to have an airport / skyclub agent who can reactivate you on the upgrade list with UP1 priority (first class ticket, but seated in main cabin) instead of the standard UPGR medallion upgrade. Once they do this, you'll wind up at the top of the upgrade list. Other thing you can do is keep an eye on the flight, and the moment a seat in F opens up, contact Delta and ask to be assigned into that seat.

May need to try a couple agents before finding somebody who knows how to type away in DLTERM - in the ATL airport one day it took me 5 agents until I got one who was willing to help me during an IROP.