I also purchased a 2018 PHEV. I did have troubles connecting the APP due to low WiFi signal.
Using a Samsung S4 and it finally registered when I did it at home. Works fine now.
Remember to follow instructions.
1) Open and close Diver's door
2) Press Vehicle start button without pressing brake pedal
3) Witin 10 secs, press lock then unlock buttons on remote, 5 times each.
4) Vehicle will beep
5) Enter Registration info. SSID then password found in plastic bag in manual.
6) If wifi signal is strong you should get a Successful message.
Good luck and let us know if you get the App to register ok.
Just wish this APP had more Functions.
I will be installing Watchdog when the Bluetooth OBD adapter arrives