"Failed to load tileset data"

So I'm having a HUGE problem here. Right before the end of the IGMC...

My project file won't open.
I've looked around and tried what people said. I've made a new project, copied the files one by one, replaced whatever data failed from a new project etc.
But now this happend:

I wanted to replace the tileset data from a new, working project. It should work, right? No, it doesn't.
No matter from what project I copy the tileset data, it still gives me the same message.

What should I do now?!

UPDATE: I was somehow able to save most of the data after all (I don't know how though ^^°) But some maps and their events still aren't working. I'll try to see if I can save them, too, but luckily those maps are the ones with the least important events.
So if anyone has ideas how to get back map files, please tell me ^^° I've managed some, but not all.

(And before anyone says it: Yes, I was stupid for not making a back-up^^°)

Hmmm... I think I had a similar situation to you once.

I would click the little RMMV house icon thing, but would say it was messed up and refused to load. What I did, and it worked for me (also without losing anything) was I replaced the file Game.rpgproject with a replacement one from one of my older versions of my game.

NOW WAIT--before you do this... this was just an idea I had that managed to work in my favor. IF this is not what you're needin' then maybe someone else would be better suited to help. Just tryin' to provide my similar situation with ya.

PS: I don't think you're stupid, darlin'.

Well, I'm using VX Ace and not MV ^^° So I don't know if it would work the same way.

Yeah, I saw that too... not certain if it's similar or not, I own ace, but never used it before.

Regardless--I hope you manage to retrieve your game. Here's me hopin'.

Well, you should surely check all the maps one by one.
What Tileset are they using?
Then check if those all tilesets actually exist.
Also if you are using preload managers, please consider testing without them, to see if the problem is solved.

STeam version? If so this happened to me last IGMC I entered, as the cloud version and the HD version were not in synch. I had to desynch the cloud to get it working again, and that was NOT easy.

The other option is if you still have your game.exe and can run it, run it and keep it open and just manually redo everything with that file open to remind you how everything goes. It will take a while, but it's still faster than starting over completely.

Otherwise, afraid it's start over time, or recover what you can.

I've been able to recover most of it, though I had to remake all the events in the missing maps (luckily I'm using parallax maps, so I didn't have to remake them from scratch XD) all items and scripts. But the thing I was most worried about, the events, were about 90% saved^^