Cannot access drive attached to the router via VPN (RAX45)

I am able to access my home network via OpenVPN which is setup on a Synology NAS. However, when I tried to access the drive attached to the router (RAX45), I got an error message saying it is not accessible. I tried either IP address or drive name, i.e. READYSHARE. Neither worked. When the computer is connected to the home network directly, there is no problem to access the drive. Is there anything to setup to access the drive attached to the router when connected via VPN? Thanks in advance!