The Wi-Fi sign-in page does not appear
Phones look for the sign-in page by opening a plain web address. Private DNS, a VPN or a saved secure page can stop that.
What to do
- Turn off any VPN and "Private DNS" in the phone's settings while you sign in.
- Open http://example.com (with http, not https).
- Forget the Wi-Fi network and join it again.
- Owners: in Settings → Sign-in page, check the page is published and the gateway is online.
Did this solve it?