App won't connect if phone connected to other, non-registered SSID / WiFi

I have a strange problem where:

  • if I’m at home (with a WiFi SSID configured in the app), it works using the “internal” URL.
  • If I’m out and using 4G data, it works using my external HTTPS
  • But if I’m say at a friend’s house, on their WiFi which isn’t registered as an SSID in the app because it’s not my network so the internal address isn’t available, it just won’t work.

I would expect the app to attempt to connect with the external URL over WiFi if the WiFi SSID isn’t in the list. It’s as if as soon as the phone is on WiFi, it will only attempt to connect to the internal URL, even if the WiFi SSID I’m connected to provides internet access and of course cannot reach my internal URL.

Accessing over the “public” URL via HTTPS works fine via browser. If I disable WiFi on my phone and switch to 4G, it works in the app.

My HTTPS is a valid LE certificate so no issues there.