Un-closable Popup

Launching the Minecraft app presents me with an un-closable popup with no options. Closing it only brings up another blank popup. Unable to click any buttons beneath.

UPDATE: Video attached. Still having issues - you can click now, but it immediately closes as demonstrated in the video. Not shown is that the black window that flashes up in the first picture I included flashes for a brief moment and disappears (my screen grabber can only do the Minecraft process itself).