Looks like I've fixed the problem. I ran OneDriveSetup.exe from C:\Windows\System32. I got a message saying that an update was required, the updated file was downloaded, run, and all was ok...

In my case, the Onedrive icon is missing even when showing all icons. I think the damage was done by an over-zealous PC Cleanup utility. I was hoping that there would be a service I could start or a...

Not that it's any help, but I have exactly the same problem. I also don't want to reinstall Windows 10 as I've spent weeks getting it to look like my old Windows 7 setup. I'm amazed and annoyed that...