1. Check your internet connection – Make sure your internet conneciton is stable, reliable, and fast enough to support OneDrive syncing.

2. Make sure OneDrive can access your network connection – For instance, if you’re using a VPN or a work network, check that your IT admin has enabled the necessary access.

3. Check your firewall or antivirus settings – Make sure your firewall or antivirus software is not blocking the OneDrive sync client.

4. Check the availability of the OneDrive service – Also, check if the OneDrive service is available on its end. You can always check the service health on the Microsoft Service Dashboard.

5. Uninstall and reinstall OneDrive – Uninstall the OneDrive app from your computer and then reinstall and configure it following the official instructions.

6. Make sure the filename length isn’t too long – Make sure the filenames in your OneDrive folder aren't too long.