An unexpected error occured

[M4DMAXX]

Hey

I tried to convert an .litematic file, I read about .nbt should not be bigger then 48x48x48 But no matter which format I choose, it fails with the unexpected error message.

I first had problems to run the program, but that was caused by me, who had still running a Java Version below 21. But I have no Idea, what causing this Error.

Thanks for any Advice