Hello, as others have mentioned, you need to set Elimination Score to something higher than zero. Additionally, you need to set HUD Info type to ‘Score’.
I just created a new project in UEFN and used the Simple Island template. I updated ONLY these two settings, launched the session and it displays as expected.
It will not show in Edit mode, you need to start the match.
If that doesn’t work, you can also try deleting hte folder where UEFN saves cached data. You can find it here C:\Users\YOURNAME\AppData\Local\UnrealEditorFortnite\Intermediate\ValkyrieUploadTemp
After you delete the folder, restart your PC and open UEFN and try again.