After adding files to your OneDrive for Business folder, one or more files may not upload for a number of reasons, and you may see a red and white "X” overlaying the file’s icon, or a red and white "X" on the OneDrive icon in the notification area:
Try the following steps to help troubleshoot file upload issues with OneDrive for Business.
Check the action center
Click on the blue OneDrive cloud in your system tray and look for errors with the files you are trying to upload in the action center. OneDrive will suggest on how to resolve some errors.
Rename the file
OneDrive for Business has some unsupported characters, strings and other restrictions. If the files you are trying to upload contain those restrictions, rename the file to remove the restriction and try to sync the file again.
Read more about Restrictions and limitations when you sync files and folders.
Move files out, sync, then move files back
Remove the file that isn’t syncing from your OneDrive folder (for example, place the file on your Desktop). Once you’ve confirmed that all remaining files are syncing, move the file or files back into your OneDrive folder and see if the file syncs.
Make sure the file isn’t in use
Files opened by an application cannot be synchronized (except for Word, Excel and PowerPoint files). Make sure that no applications are holding the file in an open state.
You may need to close the application that the file was opened by. In rare circumstances, you might need to restart your computer to allow the file to be unlocked by an application so it can sync.