Cannot access Volume #1 in File Manager

[DavidP318]

As the title states, I cannot access Volume #1 in File Manager.

To provide some needed context, I've been using my TNAS F4-210 specifically for Plex. I have two almost completely full 8TB HDDs running. At some point, the TNAS was accidentally unplugged while it was running, and as a result one of my HDDs became inaccessible for a couple months, and Plex was unable to play any of the movies and TV shows I had downloaded to that specific drive. Recently I discovered after restarting the TNAS that Plex is now able to play all of the files I thought I'd lost. It even shows that the drive is good, and displays how much free space is left and everything. But I cannot open the drive in File Manager to access any of the files on it. If anyone could help shed some light on the problem and/or provide a fix, I'd greatly appreciate it.

[TMzethar]

Plex and even some system modules need to rely on your volume 1. Please do not fill up your main volume (usually volume 1).

[DavidP318]

Okay, so should I get another drive and dedicate it solely to those system modules? There is still 20GB of free space on that HDD that I haven't filled and had no intention of filling, so is that enough?

That aside, is there a fix for my issue? Like I said, it hasn't hindered me from using the drive and being able to still watch my shows and stuff on Plex. But while I can access my second drive through File Manager on the browser without a problem, it's as if my first drive doesn't exist when I try to access it or even search for files I know for fact are stored on the drive.

[DavidP318]

So... nothing?

[Gremlin]

You are not giving anyone much to work with. So, we know the model but:

What version of OS?
How are drives arranged? 2 x single? Some version of Raid?
Which file system? BTRFS or EXT4?