Hi Community,
We encountered a situation where a users UPN was changed. And after that user was not able to sync his SharePoint library.
OneDrive was syncing thought, but when the user tried to sync the SharePoint library we found an error that the library is already syncing.
Later isolated that Issue was not with SharePoint profile.
Resolution:
Go to https://youdomain-my.sharepoint.com/_layouts/15/settings.aspx > Site Permissions > Grant permissions > Add affected users new username > Show options > Select Visitors (Read) > Share.
Repeat the process and this time select Members (Read) under Show options > Share.
Try to sync SharePoint library.
If the issue persists, go to the site where the library resides (which we are unable to sync) > Site Settings > Site permissions > Grant permissions > Add new username > Select Read permission > Share.