This is also very important for 1903/1909 as the context menu can also drop off because of this:
"What causes this is quite simple. A few months back, MS changed the way the installer works. Default settings now are per user, and not per machine. If you simply download the OneDrive installer, and instead of double clicking to install, go to the command line, run the installer like this: "OneDriveSetup.exe /allusers". Once you do that, reboot, and your context menu and all features will be back. "