Hello!
Since couple of months I cannot play SCII - instead of a game I got constant black screen. Music is on, when I move mause all tones are on, but the screen is black. By minimize to taskbar I can see that game has enormous resolution.
Had the same issue, found a solution:
In the Blizzard app, g oto the game site, then click on the cogwheel besides from play. There, go to gamesettings and then click “Reset In-Game Options”
Cheers 