Windows 10: System Protection turned on, but won't save restore points on OS drive

I'm running Windows 10 Pro on a Dell T7910 Workstation housing 8 drives. I have System protection enabled on all of the drives with max usage set to 20% on each drive. I am able to create shadow copies on all of the drives EXCEPT the OS drive. Obviously, that's the most important one when it comes to saving restore points so this is a problem that needs to be resolved. Please don't give instructions on how to turn on System Protection as I have made clear that it's on, and working fine on 7 of my 8 drives. I just can't figure out why my OS Drive keeps showing " There are no Previous Versions A

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Cannot Create System Restore Point Because Cannot Turn On System Protection

In Control Panel/System/System Properties/System Protection, "Available Drives," all that is listed is "Searching..." No drives are located, so no System Restore point can be established.

How to fix?

I have an extensive active thread in another area of the community dealing with the failure of this PC to install the latest Windows 10 update. Prior to executing the next suggested step to fix that problem I need to create a System Restore point, so a
solution to this issue must be found before I can move forward on the major problem.

YES, I have ALREADY run the SFC Command as Administrator and the report was that everything was A-OK.

 

How to delete inactive System Image Restore Points in System Restore

Windows 10 64-bit.
When I click "show more restore points" in System Restore I see a bunch of old "system image restore points" that were deleted in past and do not correspond to any currently active restore points. Clicking any of these old restore points, I simply get an error message saying they could not be found, and to select another restore point instead.I would like to delete these restore points listings but have been unable to do so.
So far, I have tried steps mentioned below without any luck :

Disk Cleanup through (C Properties
Disable System Protection (OFF and ON) in System Protection for OS (C
Disk Space Usage to minimum (slider button all the way to the left then 'Delete all restore points for this drive'),
Delete all shown Restore points in CCleaner (the problem ones do not show here),
Reset Windows Backup to Default in Windows 10 with 'Reset_Windows_Backup.bat' utility.

Any suggestions highly welcome.

 

System Restore Point Questions

1. This system has a C: boot drive and a D: data drive. In the System Protection dialog, selecting Confiture for D: brings up "System Protection for Data Drive (D." Does turning protection on for D: just use space on D: to store restore points for the whole system? Or does it somehow protect something on D:
   
2. I want to restore from a restore point that is no longer on the computer. But it is on an image of the C: drive created using Acronis True Image. If I use Acronis to mount the image under another drive letter, is there a way to get at the restore point? System Restore doesn't see that drive.