WHY WON'T LOSSLESSSCALING WORK WITH FORTNITE

Literally when I try to use losslessscaling with Fortnite it never works. I either get a white screen or a single frame that doesn't change. I change rendering settings still nothing. But when I see other people doing it it works perfectly. I am using an RTX 3070 Ti sO it should be able to do this scaling while running a cpu intensive game.