I think this is due to authentication issues:
1. Can you ping the 'Server'?
2. Are the user creds the same for both internal and external.
If not, validate if the share has permission for external users
3. Check the event logs on the RAS server to see if there is any event
logged for external users.
If all these are fine, can you do the following before you net use:
ping -n 20 server
If this doesn't work, could you send the following: (after connecting from
the external site)
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