After Selecting What to Sync & Applying, 'Sync' Option Not Enabled; No Way to Kick Off Sync

When I select what to sync, the estimated storage used bar at the bottom will fill and I can apply the changes, but after I do, the 'Sync' button ("Apply" becomes the "Sync" button) is grayed out and not clickable. The estimate bar also resets to nothing on the iPod (I just did a factory reset to try and solve the problem to no avail), and clicking "Done" (the only other available option) doesn't kick off a sync process. The estimate bar continues to stay empty until I make changes to what I want to sync. It only fills up when I make changes, but goes back to empty every time I apply the changes.

I tried restarted iTunes, restarting my computer, and restarting the iPod. I'm using the latest software for both iTunes (12.4.3) and iPod (6.1.6)

Device: iPod Touch 4th Gen iOS 6.1.6, newly reset (Sync wasn't working prior to the reset either; I was hoping resetting would work)

Computer: HP Envy dv7-7212nr running fresh install of Windows 10 (previously running Windows 7. As of about 3 months ago, when I last ran a sync on this OS, it worked in Windows 7. May have had older versions of iTunes and/or iOS though)