The TL/DR is that unless you’ve set it up, you can’t reach your HA install from outside your home network. You need to do that if you want your phone to be able to report where it is (using the app). You can do that with the (paid) Nabu Casa cloud service, or do it for free.
You can, of course, use other methods for home/away, such as Bluetooth, that don’t require remote access.