Oft times you are correct. Modern technology also adds the "magic" component, where things should work, but don't. Where it used to be "stupidity is doing the same thing over, and expecting a different result", with technology, this is provably false! Success is sometimes stubbornly persisting, doing the same (supposedly correct) thing until it starts to work!  ;-)

With some embarrassment, I have to confess that this may have been caused by a loosening power cable on the RAID. I noticed that after I accidentally bumped it (it sits in an adjacent room because of the noise). It has come up every time ever since then. 

In my many years of working in technology, I still find that 90% of troubleshooting for myself or the people I support can be resolved in two basic steps:

1. Is it turned on?
2. If it's turned on, is it plugged in?

Thanks for your support!

Ric

If the driver is not loading, then there is no volume to mount, correct. the kmutil should work in these cases in Big Sur.

It is just a driver extensions install. (upgrades a file in your system)

there is no danger to your disks.

Try this terminal command:

sudo kmutil load -p /Library/Extensions/SoftRAID.kext

Note:
The "up" key in terminal will show prior commands, so next time you want to manually load SoftRAID, just hit the up arrow and this command will be available without having to type it.

You may need to do this until Apple fixes this bug.