It’s my understanding that all the IP addresses have to be on the same subnet, so yeah, find out what your main computer has in the way of IP address, then find out what your Android device has ( make sure it’s connected to your local router - not the mobile phone network ).
When I configured mine it was as follows:
Main PC ( Server / Game Machine 192.168.1.96
Android Device ( get this from the device itself, or your hub where it’s connected wirelessly 192.168.1.170
Press the “Set” button on the android app and just accept the defaults.
If there are multiple IP addresses in the server software, just select the one that is you main WiFi connection and the same format as the android device.
Close the app. Slide it shut ( extra safe ) . Close down the server. Start the server. Start the app.
Then things should be okay.