Not able to sync OneDrive client with Sharepoint - on premise while proxy enabled
Having investigated the request, please refer to the below, for Microsoft OneDrive and SharePoint.
How the Microsoft SharePoint Server is deployed (HTTP or HTTPS). Symantec recommends reviewing the Microsoft Support website in the first instance.
The SharePoint server is setup for NTLM authentication. NTLM authentication is designed to take place between the client and server (point-to-point protocol) with no intermediary terminating device, such as a proxy. If the SharePoint server supports both NTLM and BASIC authentication, then the browser can still successfully authenticate while proxied using BASIC authentication.
Note: It's recommended to obtain guidance from Microsoft, before passing SharePoint-destined traffic through Edge SWG.
If you are using authenticated proxies, it is not supported in OneDrive.
Specifically, with syncing OneDrive with SharePoint, policies will have to be created in Microsoft GPO to bypass the Proxy, for user traffic destined for OneDrive. This has been validated on a use case.