External USB drive not showing up on LinkStation SoHo 720 NAS

[Hostirad]

One reason I bought a LinkStation SoHo 720 NAS is the USB port for attaching an external drive. I had been using a Western Digital Elements 2TB external drive (WDBAAU0025HBK-01) as a shared network drive, attached to the USB port of a Linksys EA7500 router. It is set up with Samba 3.0.37. When I upgraded my router to a Linksys LN1100, I needed a new way to connect the external drive to my network because the new router does not have a USB port. Because the LinkStation SoHo 720 NAS does have two USB ports, I figured that I could simply plug the WD external drive into the rear USB port of the Linkstation. But when I tried this, I could not see the drive when connecting to the LinkStation through the web interface, Storage - USB Drives. (The primary hard drives in the LinkStation show up just fine.) I tried shutting down the LinkStation and starting it again, and the USB drive is still not visible. I disconnected the USB drive and reconnected to my old router, and it shows up as a network drive just fine. The drive is also readable when plugged directly into my Windows 11 laptop. Any ideas on making the external drive visible/accessible?

[Hostirad]

I might add that I tried an 8GB HP Thumbdrive and unpowered Western Digital 4TB My Passport Drive, and both were instantly accessible through the LinkStation.