Trouble adding my nas network drive to Plex library

Router Firmware: V1.0.2.32

Nas: Synology DS1815+ (Named Vault)

I've been following this guide https://kb.netgear.com/000038628/How-do-I-use-my-R9000-Nighthawk-X10-to-add-a-network-drive-to-my-Plex-media-library and when I get to step 9 "The network drive is added and you are redirected back to the main Plex Media Server page." I am not redirected back to that page, instead I am returned to the same page:

However the connection I just added does appear in Plex, but no media is ever found. Here is an example of this:

The username and password is that of my nas, using any other returns an error. The dvds folder is on the root of one of my nas drives. The IP of the nas is correct. I click apply, it says please wait a moment, then I am returned to the same page, however 'DVDconnection' is now found in the Plex add media section.

So I go into plex, add library, add movies, add folder, browser for media folder, choose DVDconnection (it does not show any subfolders even though they do exist)

then add library and get "there are no items in this library" after scanning for a second. I also created a connection called fakefolder for a folder that doesn't exist on the nas and I get the same result.

Cannot edit or delete a drive connection from the router settings, my added drive connections displayed in the image above are not seen in the router settings:

I already have Plex running on my nas before buying the router so I know the media is compatible. Here is a screenshot of it from the plex on my nas:

I can access the files from windows explorer.

Permissions for DVDs

File services:

Bought this router especailly for plex because the nas can't transcode very well. I'm not sure what I'm doing wrong. Thank you for reading and I will appreciate any suggestions.