Remote office can ping the server, but shared files will not open
Connectivity appears healthy because the server responds to ping, yet users cannot reach the SMB share by name or mapped drive.
Separate basic IP reachability from DNS, TCP 445, domain authentication and name-resolution paths. Test the server by hostname and IP before changing anything broad.
The goal is a precise fix to the failing layer instead of rebuilding the VPN, server or workstation unnecessarily.