If the fixes for the specific OneDrive Access Denied error don't help then here are fixes for OneDrive sync and to check over and repair the App itself:
1) Try these fixes for OneDrive sync:
https://support.microsoft.com/en-us/office/fix-...
https://www.windowscentral.com/tips-help-you-fi...
https://windowsreport.com/onedrive-sync-problem... (Avoid ad links which intrude into editorial copy, especially avoid Restoro ad)
https://helpdeskgeek.com/help-desk/10-onedrive-...
https://www.thewindowsclub.com/onedrive-sync-pr... (Avoid ad links which intrude into editorial copy, especially avoid Restoro and Reimage ads)
http://www.rawinfopages.com/tips/2014/09/fix-mi...
https://www.multcloud.com/tutorials/onedrive-no...
2) Try resetting OneDrive here:
https://www.thewindowsclub.com/reset-onedrive-i...
3) Right click OneDrive cloud icon in System Tray at right end of Task Bar, choose Settings, then Accounts tab, then Unlink OneDrive. Restart PC, go into Start Menu to open OneDrive sign in again to see if it stabilizes. Tutorial here:
https://www.tenforums.com/tutorials/36246-link-...
4) If not then Uninstall OneDrive in Settings > Apps > Apps & Features > Microsoft OneDrive. Restart PC.
Then reinstall OneDrive from a fresh download here:
https://www.microsoft.com/en-us//microsoft-365/...
If you prefer the OneDrive Store app then you can re-register it from Option 2 here:
http://www.tenforums.com/tutorials/3175-apps-re...
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If you want to keep your Documents, Pictures and/or Desktop folders sync'd in OneDrive you can use Folder Protection/Backup in OneDrive settings as shown here:
https://www.tenforums.com/tutorials/116029-turn...
If you want to save space and keep your files in the cloud with only links on the hard drive to download them, use Files on Demand here:
https://www.pcworld.com/article/3233488/windows...
I hope this helps. Feel free to ask back any questions and keep me posted. If you will wait to rate my post, I will keep working with you until it's resolved.
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