A Microsoft file hosting and synchronization service.
Dear NeilsMum,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
As per your description, please don’t worry, we can work together to narrow down and resolve the situation.
Firstly, may I confirm what kind of files are you trying to sync? There are some restrictions and limitations with the OneDrive sync.
For reference: Restrictions and limitations in OneDrive and SharePoint (microsoft.com)
Please try if you could sync the files with the OneDrive web version. If you could sync the files with the web version, then please try if you could sync other files to the OneDrive client. If other files have the same issue, please reset the OneDrive client: Reset OneDrive (microsoft.com)
Your understanding and patience will be highly appreciated. I hope that you are keeping safe and well!
Sincerely,
Sean Cai | Microsoft Community Moderator