I called Microsoft and determined the USB transceiver was not working. They said they will replace the keyboard, mouse, and USB transceiver for free. I just needed to give them the product ID from the bottom of the keyboard and they give me an RA number.
Once they receive it they will send me a new replacement system.
I have the 5000 model and the transceiver is a 2.4 Ghz v6.0. By the way, I have had this system for about 3 or 4 years. They said you cannot buy the USB unit by itself. It will only match up with the original keyboard and mouse which is why you cannot
buy the USB transceiver by itself.
For now I will just connect a "wired" keyboard and mouse. This is definitely the least expensive option and I can continue using what I consider to be nicely balanced ergonomically.
The number to call is 1-800-360-7561.