This provider does not support specifying a folder as data source - Office 365 Fast File Sync Provider

rror Example:

Verification failed: Error reading from entity '<entityName>': This provider does not support specifying a folder as data source. Please adjust the connection string to point to a document library.

Cause:

You are trying to use the 'Layer2 Data Provider for Office365 Fast File Sync' to a specific folder in the SharePoint library. This is not supported and you need to sync to the library root instead.

Resolution/Workaround:

You cannot use the 'Fast File Sync' provider for syncing to a specific folder in the SharePoint library. You can instead use the standard 'Layer 2 Data Provider for SharePoint (CSOM)' if must do this. Otherwise, you must sync to the library root.