Cannot delete a subfolder

I wonder why I cannot delete a subfolder on my host. I get "550 Directory not empty" error but the directory is empty or at least I don't see any files in it. Any idea?

I also cannot change the permission, it would give me " 550 Operation not permitted".

Hello ..

It looks like a permission problem to me. Your web hosting provider can very likely help you with that.

Regards,
Mat