If you see an alert in the app indicating that you should "check your internet connection and try again", please review the following:

Verify that you are connected to WiFi

If you are on public WiFi (e.g. Starbucks), ensure that you are properly signed in to their network. Sometimes pubic WiFi networks require users to sign in via a browser popup before WiFi is actually enabled for your device.
Check that Airplane mode is not enabled and that WiFi is turned ON
Try streaming a YouTube video or searching Google on your phone. If these aren't working either, there may be a problem with your WiFi network.

Verify that Cellular Data is turned ON