Star Alliance upgrade on UA codeshare flights?

I have a flight that includes a Lufthansa leg as a UA codeshare flight.
Is it possible to use miles as a star alliance upgrade award on that flight?
I tried doing it on this site...
https://www.united.com/web/en-US/app...rdUpgrade.aspx
But it always fails.
Are agents able to help me with this?
TIA