Check if the following registry key is present and set to 0. If set to 1: there's your problem. Just change the value and it should work right away, without reboot.
Or run the following Powershell command in an elevated shell:
Set-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\OneDrive' -Name DisableFileSyncNGSC -Value 0
If the key doesn't exist it is equal to 0 in practice.