If the icon is there and you are now signed in again click on the icon. A pop up panel will appear. Click on the cogwheel top right(settings for onedrive) When the new panel opens you will note a row of other options that have Settings. Account. Back up. Network. Office. About. written in them. Check the settings box again. In there make sure that you have the "Start One Drive Automatically when I sign in to windows" box ticked. I have all the boxes ticked and have no problems.