Keyboard partially stopped working today

To clarify - All number, letter, and symbol keys work fine.  Tab, shift, control, alt, windows key and caps lock also work fine.  Using the function key to lower or raise volume, stop and start songs, etc, do not work.  The enter key does not work.  Certain multi-button commands such as alt+tab do not work, despite the keys working when pressed alone.

 

I have tried factory resetting the keyboard with switch #4 on the back - to no avail.  I have tried every USB port on my computer, as well as different usb type-C cables, all to no avail.