Server side alerts are delivered via push notifications, not via e-mail. If in your mobile device settings, notifications are enabled for the app, then you will receive alarms notifications even if your app is not running (as long as you are not in the "Airplane mode").
For iOS just go to Settings app > Notifications > In Notification Center > Trade Interceptor > and make sure notifications are activated according to your custom settings there- style, sounds on/off etc.
For Android OS it is more complicated.
Please note the following points below and points #2 and #4 do not help, let us know.
1. Do you use some kind of a task killer or something that kills the apps and services on background?
2. After 10 unsuccessful attempts to connect push service will be disabled and users should try to reconnect manually from App Setting->Push Notifications - tap on the button to retry the connection (again in 10 attempts).
3. Google play service should be installed and running on the device.
Check if google GCM service is running from device's Settings -> Apps -> Running -> Google services
There should be an item labelled - GCMService
4. Try to restart the device as the GCMService might be corrupted.