Permission problem in a sense. It's always a permission problem. But you would get the same error if the target file system isn't physically writable. If you click on the error message, then you can copy & paste the complete error message. Maybe it says something interesting at the end that's cut off. Maybe not.
Bottomline is that FileBot asks the OS to move A to B, and the the OS says Access Denied, and then FileBot passes along the error message. So FileBot doesn't really know what the underlying problem is either. And probably neither does the OS which also merely delegates the instruction to your 3rd party file system driver.

The source of the problem is likely OSXFUSE / SSHFS so the next step would be to ask around in those communities on how to best debug things. There's probably some logs somewhere, or logs that can be enabled, to help you see what's going on and find a solution or workaround.