I personally never use the native Microsoft backup utilities, choosing instead to use third party options, so I might not be the one to help you with this, but.....
So you don't think that you're being ignored.....
Everything that I'm finding around the web would seem to suggest that, that particular problem is indicating an issue with the backup device (hard drive) you are using and most of that information suggests that a DiskPart clean (wipe) of the drive followed by using Disk Management to re-initialize the drive, partition and format it has helped them overcome the problem.
The only thing that I would add to that is.... Use extreme caution when using any utility to clean / wipe a drive and be sure that you are directing you activity towards the drive that you want to wipe. An error of selecting the wrong physical drive could be very problematic.
There are a few members here who do use the Windows backup programs, so you might want to wait for someone who might have some specific knowledge of that error and a possible suggestion for you to overcome it.
I did a manual backup of the System Image yesterday and it worked.
Whenever I do the "Setup Backup" I get the same popup no matter what I try to backup. It appears, to me, that it is telling me it can not do Backups on a "schedule!.
Perhaps another clue is that I used MS Backup when this computer was still running Windows 7!
Donald I use Windows backup for incremental backups of "My Docs" Acronis for System Images.
Windows backup is most likely looking at the last backup settings (Image) you performed.
To set a backup frequency (Not an Image) Open Windows Backup > Click on "Change settings" select the drive letter (X)
"X" is the destination where the backup is to be saved > Select what Libraries or user files you want to backup > click "Save and exit. The backup will automatically start. If you wish to perform incremental backups make sure you set the time and frequency schedule while you are in settings.
Maybe I am misunderstanding your exact situation but you have not used the Windows Backup to do a File backup before? Your only option is to set it up and when you try it errors with the file not found error?
If that is the situation, maybe there is some corruption in the utility itself and something is missing or not accessible. You might want to run the System File Checker to scan your system. Maybe it will find some type of problem. If that doesn't find anything you could try the trouble shooter to see if it says anything.
So open an Admin command prompt window and type the command below. It will take some time and give you a message when it finishes.. Let us know what it says.