Navigate to the settings tab marked by the gear in the bottom right corner of the application. Find your "Alarm Volume" setting and make sure that is turned to maximum. After doing this, please scroll down to "Wake Up Phase". Please select the "0 minutes - normal alarm" for an alarm that rings immediately.
Check your settings by tapping on the gear icon and make sure that your alarm volume is turned all the way to maximum. Set the wake up duration at the very bottom of the settings page to 0 minutes for an alarm that rings immediately.