Having the game open in fullscreen and then unplugging a secondary monitor
(I plugged mine back in during the video)
will mean the game refuses to reopen from being minimized

Since the video is a bit unclear since OBS will black the screen for a bit after changing what application you focus on, I'll quickly explain what I do in the video:

I play Minecraft in fullscreen, unplug and then replug my second monitor's HDMI (you can hear the sounds), and then tab out of the game. I then try to reopen the game back into fullscreen to no avail.