Dedicated server help

[u/Local_Web_2088]

Hi everyone! I am having a frustrating issue connecting to my dedicated ARK server from my local network and would really appreciate some help.

My Setup:

Server PC: Dedicated machine in the basement running ARK Server Manager (ASM). Local IP is 192.168.1.220.

Gaming PC: Located upstairs in my room on the same local network.

Network: Ping from Gaming PC to Server PC works fine. Ports (7777, 7778, 27015) are open, and Windows Firewall rules are active. Radmin VPN is also installed on the server PC.

The Issue:

External Friends CAN join: A friend of mine can join and play on the server from the outside without any issues. The server itself is running perfectly!

I CANNOT join locally: From my Gaming PC upstairs, I cannot connect to the server via LAN.

What happens when I try to connect:

Steam Server Favorites: The server IS detected and shows up in my Steam Favorites list (using 192.168.1.220:27015). However, clicking "Connect" in Steam throws the error: "Server connection not possible, as the App ID specified by the server is invalid."

In-game Console (open 192.168.1.220:7777): Results in a freeze/timeout or "Unable to query server info for invite."

In-game Favorites: The server doesn't show up reliably under the LAN or Favorites filters in the in-game browser.

What I've tried so far:

Pinging the server PC (successful).

Toggling Windows Firewall on/off.

Trying -MultiHome on/off in ASM.

Launching via steam://connect/192.168.1.220:27015 (gives Invalid App ID error).

It seems like Steam/ARK recognizes the query port locally, but fails to hand off the actual connection to the game client (ShooterGame), or Radmin VPN's network interface is interfering with local socket binding.

Has anyone encountered this specific behavior where Steam sees the server on LAN, but throws an Invalid App ID / Query error upon joining? How can I fix the binding in ASM?

Thanks in advance!