Problems accessing network resources through VPN?

Question

VPN

There is a remote computer running Windows 7, which is in a workgroup
There is a Mikrotik with configured pptp
Connecting via VPN
Trying to access a network resource, it asks for credentials
Enter the domain user data in the [email protected] format Access is denied Enter the
domain administrator data everything is fine
For checks, we give the user [email protected] the rights of both the administrator and the domain administrator, but this does not change the essence.
What can be wrong?