Assistance auto connecting to device over VPN

Apologies in advance, this post will be slightly vague because it's work related but also because I'm sonewhat out of my depth.

At work, we have access to multiple remote cabinets via a VPN. The primary device within these cabinets is running Linux. Attached to this primary device is a secondary device connected to the primary device via Ethernet. To make changes to this secondary device we have to use proprietary windows software and be plugged into the secondary device in person.

Today I got the idea that this device should theoretically be remotely accessible like any other device in the cabinet. First, I hooked up a travel router to the secondary Ethernet port on the device. Sure enough, connecting wirelessly to the travel router network via my laptop allowed me to connect to the device and run the proprietary windows software wirelessly. Good first step!

I then disconnected the travel router and ran an Ethernet cable between the secondary device and the cabinet switch. Theoretically, the secondary device should now be accessible via the VPN. However, the problem is with the proprietary software. When you open the software, it auto finds the device via IP. If it doesn't auto find it, there's no way to connect.

When the secondary device is plugged into the cabinet switch, the software on my laptop does not auto find the device. However, if I'm plugged directly into the device, or on a wireless network plugged directly into the device, it does auto find the device. It's like the .Net software can scan my wireless card or my Ethernet card for the IP or specific device info it needs, but once on the VPN, it can't find the device remotely.

Does anyone have ideas? It's like I need to create a virtual windows Ethernet device and somehow mate it to the IP of the device behind the VPN. Then when the windows software scans available cards/connections, it will find the device.

Any suggestions? Am I way off? Thanks tremendously in advance for the help.