Check through this list to see if any of these items solves your problems.
Ensure that your phones and PC or Mac are all on the same local network. The PC or Mac does not have to be on WiFi, but must be on the same local network.
Make sure you are on the ‘Start Campaign’ screen on the Core game while trying to connect.
If you PC or Mac asks you for permission for this app to communicate through your Firewall, say ‘Yes.’ It may ask you the first time you run the game.
Try turning the Controller app all the way off and on again if it persists in not connecting.
While in the ‘New Campaign’ screen, backing out to the Main Menu and back in often helps refresh the server list.
If the controller app still cannot see the Core game, you can use apps like Remote File Manager on iOS to determine if your phone can even see your PC or Mac. For Remote File Manager specifically, if you hit the + beside “Dashboard”, then select “Network Share”, at the bottom you should see “NETWORK NEIGHBORHOOD”. If your PC or Mac does not show up on this, it means your phone cannot see your PC or Mac. To remedy this, ensure that network sharing is On (http://windows.microsoft.com/en-US/windows-8/turn-sharing-on-or-off), double check your firewall settings, and ensure your router bridges the wired and wireless networks into a single network.
If the controller app can see the Core game, but you cannot connect, or it does connect but immediately disconnects, check to see if you have any network management software such as “Killer Network Manager”. If you do, either add exemptions for Eon Altar to them, or just kill the programs. Killer Network Manager, for example, has two processes, “NetworkManager.exe” and “KillerService.exe”. Ending both of those tasks may allow the game to stay connected.
If the game persists in not connecting, start a new discussion in our Steam Discussions to chat further with the team.