Hello,
I suggest that you may check the options below:
VPN Server Configuration: Check the settings on your VPN server, and ensure that it is configured to accept passthrough authentication and that it is communicating properly with your on-premise Active Directory.
DNS and Domain Configuration: Verify that your DNS settings are correctly configured for both the on-premise network and the VPN network. Ensure that the VPN network is able to resolve domain names for your Active Directory domain.
Group Policy: Review any Group Policy settings related to VPN authentication and ensure that they are configured correctly to allow passthrough authentication for DFS shares.
Event Logs: Check the event logs on both the client and server side for any relevant authentication or networking errors that could be impacting the passthrough authentication.
Best Regards,
Hania Lian
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