Dear Jayne.G.Buderim,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
As per your description, you are having issue with OneDrive sync, error prompts that "too many files"
If the understanding above is right, generally, as per the official article shared, for better sync performance, it is recommended to sync no more than a total of 300.000 files across the cloud storage.
For your reference: SharePoint limits - Service Descriptions | Microsoft Learn
Restrictions and limitations in OneDrive and SharePoint - Microsoft Support


Given this, please check if the file count exceeds the limitation, if yes, please reduce the file count accordingly.
If not, please check if Reset OneDrive - Microsoft Support, Change the location of your OneDrive folder - Microsoft Support, rename the folder, move files out and move back in can help.
Appreciate your understanding that sometimes the initial reply may not resolve the situation very soon. However, we can work together to narrow down and resolve the situation. Please kindly post back and provide the more information, then we can focus on your specific scenario and provide specific suggestions.
If the understanding above is not consistent with yours, please feel free to post back and point that.
Your understanding and patience will be highly appreciated. We hope that you are keeping safe and well!
Thanks for your cooperation.
Sincerely,
Rhoda | Microsoft Community Moderator