Hi Bob,
We're understanding that on your Mac Pro, the Bluetooth icon in the Menu Bar is stating "Bluetooth not available". Let's investigate.
First, we can check the hardware in Apple menu > About This Mac > System Report. On the left under Hardware do you see a listing for Bluetooth? If so, click on it. Check to see if you're seeing any messages in here about it be unavailable or perhaps if the window is blank, etc.
We can also run the built-in diagnostics on your Mac. Here's how to get that going: Use Apple Diagnostics to test your Mac This will run a test on the hardware in your Mac and return results.
If you haven't already, be sure to also restart your Mac and install any incremental updates (after making a current backup). We can use that to be sure those connections and software are refreshed. We recognize that if Bluetooth isn't working, you may need to connect a wired keyboard and/or mouse to complete some of these steps.
Let us know what happens!