Can't upload worlds to my Realm.

Hi,

I've been trying for a while to re-upload my realm from a singleplayer backup but the upload gets stuck everytime with the error "Upload failed (-1)" under 1%.

I've tried restarting my game, changing the world for a smaller one (even a really small), uploading a non datapacked world, closing / reopening the realm, resetting a world for uploading on it, ...

But nothing seems to work...

I will take any help at this point, nothing seems to be evolving or getting better and the upload still fails.

Many thanks,