Check that the One Drive blue cloud is in the taskbar and hasnt got any messages.
If it has got an icon you can check what the cause is. If it is a red cross on the one drive icon it isnt syncing.
Once that problem is sorted it should go back to a normal one drive cloud.
If the icon is not there at all it is possible the machine has shut down the program. Restarting the device will resolve the issue.