When I try to use E-Upgrades to upgrade my PHL/ORD/SFO/ORD/PHL itinerary booked on UAL.com, I get the message "We could not find any open itineraries that are upgradeable".

According to my summary, I have enough E-upgrades. The fare is W07NWX. Dep is 14 Feb.

Any ideas why this doesn't work?