In the More "hamburger" menu (access from the home screen), there are three dots that indicate which services are currently available: Internet, Bluetooth and Notifications.
For best performance, all indicators should be green:
If a dot is red, the service is not enabled or unavailable, and Bluechain might not be able to process the payment or it might take longer to process.
To display the status of each service, tap Diagnostics. If Bluechain requires a service that has been disabled, the app will prompt you to turn it back on.
Although not shown on the mobile services indicator, on some Android phones, the Location service is also required.