I’m a casual player of Heroes of the Storm. Recently, the game kept kicking me out to the desktop. The game appears to have a display issue because it flickers while loading, but then ends up back at the desktop. Blizzard has not provided a solution to the actual problem, but has provided a workaround.
When bringing up the Battle.Net screen, go to: Options >> Game Settings >> Heroes of the Storm >> Command-Line. Then type:
displaymode = 1
That will put the game into “windowed fullscreen”, which helps get around the initial loading process. Once you do that, it appears that you can put the game into native fullscreen from the internal options.