Microsoft OneDrive is the popular edition to the online Microsoft 365 suite, and while as a standalone product it's worth ...

Files on one computer are automatically synced and downloaded to the Magic Briefcase folder on all your other computers. This makes it easy to drag and drop files to the folder for quick syncing.

OneDrive should now start syncing your files and folders. Once the sync is complete, you'll no longer see the red X icons next to your files.