I am also having this problem. It began once I reinstalled windows (reset PC) to wipe files etc, start fresh. I own the company and domain connected to AZURE-AD/ENTRA ID I added the PC to, and regularly signed into both profiles without any syncing or back-up issues.
During the new setup, the business account was added first, then the personal account. But it should not matter, because in either case the device is added to the ENTRA/ID.
In any case I now get this issue:

I will be contacting MS business to see if there is a restriction on the admin end that can be changed.
The problem here is I have plenty of people working for me with BYOD laptops, they have no issues connecting the devices for their work accounts, I don't set major controls that matter to most; but I am certain I cannot have the person OneDrive accounts all up and quit backing up.
Anyone else having this problem?
I will repost if I can find, or am provided a solution.
Cheers.