I was faced with this problem twice.
The first solution was:
- open EpicGamesLauncher.exe properties
- open “Compatibility Settings”
- Set “Disable display scaling on high DPI settings” to checked.
These steps solved my problem.
But a month later I see black screen again.
DPI settings was already checked.
The second solution was stopping background process “EpicGamesLauncher” in Task Manager. After terminating this process EpicGamesLauncher started normally.