Datalinq Server connects to the Dashboard panel to retrieve data, its not Dashboard connecting to the Datalinq Server. The Dashboard panel makes its data available to any Datalinq Server that connects to it.
I assume you must have Datalinq Server installed on both of the XPression systems. Both Datalinq Servers should be using the same port number and IP address to connect to the Dashboard panel.
If you are in a hurry to get this working and don't want to troubleshoot any possible issues going on, you could just add the IP address of your 'working' Datalinq Server to the Project loaded on your 'not working' XPression. XPression > Datalinq Manager > Add IP Address of Datalinq Server with working Dashboard connection