Seems I had this issue in the past, here is what fixed it:
Under the FTP site, go into 'FTP Authentication', click on Basic Auth and edit. There is by default a '\' as the directory, remove this. Click OK and exit out of the management console. You should be able to FTP in now. The problem is FTP parsing the \ as a root directory and not the user root, which creates an access denied. With the slash removed it defaults to the user profile for home directory.
Hope this solves your problem.