How do I solve SSH_FX_PERMISSION_DENIED Issue?

That error means that your user doesn't have the necessary permissions to perform the operation. I recommend logging in over SSH or LISH and investigating your permissions a bit further.

First, run the command ls -lha one level above the desired upload directory. This will show you the permissions and ownership of that directory. For example, here's the output for the "html" directory within /var/www:

drwxrwxr-x  2 root admin 4.0K Mar 11 11:41 html

Then, using this information you'll want to adjust the permissions and ownership to allow your user to upload files in the directory. If you aren't familiar with managing user permissions, I recommend checking out our Linux Users and Groups guide - specifically the sections on chmod and changing file ownership.