I was able to help someone fix it temporarily while they make an update fix. Go to your install folder where you have Fortnite_Studio. Copy everything inside there ctrl+a and ctrl+c and paste it inside the regular fortnite folder. Then with epic running in back launch UEFN from the UnrealEditorFortnite-Win64-Shipping.exe file under your install location at Fortnite\FortniteGame\Binaries\Win64