I was having issues too with the Gen 3. Someone on TMC said, keep the phone/laptop real close to the Wall charger and also make sure the single green light is blinking. Press the button on the charger if you need the wifi to rebroadcast.
I managed to connect once and input my home wifi SSID and pwd, it did a firmware update since it power cycled after a few minutes.
Couple of points I noted:
1) If you are using a phone to scan the QR code and then join the Tesla wifi network, there is no need to input the WPA2 password. It's already noted.
2) If you keep seeing the swirly thing, type in the whole address:
http://192.168.92.1/installation it takes you to the main page where you can input your wifi, change amps etc.