SOLVED: I had METERED NETWORK turned ON. It seems that Microsoft has changed how they handle manual downloads of updates via the Windows Update dialog when you have the Metered Network setting turned ON. So, I turned this setting OFF, paused/resumed/closed/reopened Windows Update and it started working again. Make sure you go into Advanced Options under Windows Update and check that Download updates over metered connections is toggled ON. Other than that, make sure you hit Pause for 1 week and then hit Resume Updates. That should work. If not, just restart.