First hello everyone !
Second I am really sorry I am very much a noob in this and I am suffering from a migraine, meaning I am going to be a idiot on two fronts.
I am using the synology 916+ as a storage device for my shield pro tv which is the server for plex which has been working fine however I have been running out of space, so I added a usb drive to my 916 and my 916 sees it fine as does my windows pc but I cannot for the life of my get plex to see it. I have as far as I am aware set the permissions correctly for the drive for both my plex user account and my main 916 user account for the usb drive but when I go to add the drive as a library in the web interface as I would normally do in plex it just shows the standard internal mounted hard drives.
My dsm should be the latest which is DSM 6.1.4-15217 Update 5