We have an Archer A7 as a DHCP server for a small peer-to-peer network.  All shared files and a Windows VPN server are on a PC at 192.168.1.111 which we call the file server.  We manually set the static IP on this PC's NIC.  This machine is old and slow, so we are replacing it.  I thought that this would be easy.

The plan was to simply assign the same PC name, IP address, and share names to the new machine as the old and swap it in.  I hoped that none of the other machines on the network would be the wiser...

It sort of worked.  The network works fine within the office, but connecting to the shares on the file server through the VPN from outside the office fails.  As I began to troubleshoot I realized that I don't know as much about networking as I thought!

The situation is this: I can establish the VPN connection no problem, and even reach the Archer A7 setup through it.  The problem is that the file server doesn't answer at 192.168.1.111, even if I simply ping it.  I can see other machines on the network by hailing their IPs, but not the file server.  I began poking around the router's interface for clues, and found many, but don't know how to interpret what I am seeing.

In addition to setting the new file server PC's IP address in the PC's IPv4 settings, I also reserved it through the router's DHCP Server's Address reservation table.  The file server PC does not show up in the DHCP Client list, either by IP or by MAC address.  It does, however, appear correctly (by name, IP, and MAC) in the Wired Client list, and under Advanced> Security> Access Control> Online Devices (although it is grayed-out here).

I don't suspect the problem is with the VPN client computer, since it worked fine for years before switching the server.  I suppose it could be a problem with the VPN server, but I can connect and access shares on the other PCs in the office.

Any idea what might be going on, or how I could troubleshoot?

Thanks!