Help Setting Up Shared Media Server Drive on Secondary Router

I am having trouble getting a Media Server reestablished on a R6400v2 router.

Previously, I had this working where I had an external hard drive connected to the USB port on my router and shared through the DLNA/Media Server settings on my router. I was then able to connect directly through computers on the network or VLC on my Chromecast and phones. It made for easy access to media files on the TV without having to build and run a NAS.

Recently, I got a Netgear MK63S mesh system (for free!), and there were some dead spots in my house, so I was eager to switch to the mesh system. Unfortunately, the mesh system has 0 USB ports and is a little lacking in ethernet ports as well. By plugging the old R6400v2 router's internet port into the available LAN port on the new router, I was able to easily keep some devices wired into the R6400v2 online without having to play with any settings. And, if I connect a device directly to the old router, VLC can still access the Media Server drive/files. But, I cannot for the life of me figure out how to have anything connected through the new mesh network even see the Media Server in order to access it.