I wouldn't know about GPE ROMs as I haven't touched AOSP-like ROMs in a long while (since my N4 days), but you might need to elaborate what you mean by "network connection" here. Is it the cellular network you can't connect to? Try checking your SIM, maybe. Is it WiFi that you can't turn on? You might need a modem zip to flash, but not sure if that's the case with GPE.