SharePoint Connector used an incorrect authentication type. Authentication failed after upgrading to version 2.4.0 of the Connect For SharePoint plugin. 

The username and password authentication was changed on the Connect for SharePoint screen with the following information.

1. Site URL. Specify the URL of the SharePoint repository.
2. Connection type.
   • • On-premises. Select this option if you have a local on-premises SharePoint repository. On-premises has only the Basic authentication type option.
     • Online. Select this option if you have a remote Office 365 SharePoint repository. Select Basic or Modern authentication type option. If you select the Modern option, you must also fill in in the following with your credentials: ClientId, ClientSecret, and Realm. 

You can switch between local on-premises and online cloud repositories and have both repositories copy files to the same media folder or different folders. See SharePoint On-Premises VS. SharePoint Online (2013).

If an error occurs more than 3 times while downloading or inserting the same SharePoint document, the processor will orphan the thread and leave it in a state of constantly checking its status.

The thread pool for the SharePoint connector is now configurable.

AppSettings  = "EPiServer:Sharepoint:MessageThreads" 

Valid properties: 1 through 16