Some Android-based devices are not redirected to the Captive Portal when the user gets connected to WiFi network with Android device. 

The Captive Portal is not triggered automatically when is the testing domain accessible.

How Android determine if it has an Internet Connection

  1. The Android devices check for the following domains which are hosted on Akamai network:
    and other domains used for this purpose by Google.
  2. If the domain is accessible and returns “generate204” code, the captive portal is not triggered automatically. “generate204” response means the device is connected to the internet