External (USB) Drives not showing when accessing via FTP

Now before everyone starts about FTP, I only turn it on when needed and only for internal use.
In the past, I somehow managed to get my external hard drives attached to my PR4100 to show when accessing via FTP.

I found the answer once and now can not remember how to do it or what needs to be done?

I have SSH access and FTP shares enabled.

Do you have FTP enabled both on the Share itself and in the Settings > General section?

As a troubleshooting step one could also enable NFS in both locations and see if that helps.