Is the behavior still the same if you reboot your Core? Also, I’m seeing something a bit strange, it appears you may be connecting to the XPS_Server via a network connection instead of a local connection (outline by the computer with the internet icon).
Do you recall how you set up the connection to this drive, did you connect via SMB by any chance? Connecting to the Core’s share via SMB can cause some weird behavior, since the Core has to connect to the share via multiple hops (Core -> Router -> back to Core).
If you try to click on “Add Folder”, can you share a screenshot of the options you are presented in the side-bar? Don’t add a new location just yet, but I am curious to see how the side-bar looks like, it should look something like this: