You've probably run into the same problem I did on the Steam version: A Node-Webkit (nw.js) profile version mismatch error triggered right as the ending movie was meant to play, and when you restarted you're actually in the room right before the door that triggers said ending but without a source of light- so it looks like a black screen.
Try walking two steps right, one step up, and then pressing the interact button/key after the game's loaded. You should be able to get the movie to play this time.
No clue how to avoid the error, personally, or even what exactly caused it. All RPG Maker MV/MZ games use nw.js and obviously the game shouldn't have magically changed its version while you were playing.