this looks a bit cumbersome... the calendar sends a notification, you listen to all notifications on the device and if there is a notification from the calendar, then you send another notification which on button click finally opens your app...
I'm not familiar with the calendar extensions we already have... it would be nice to have a calendar extension which can trigger an event...
btw. you do not need an alarmmanager in this case, the MelonNotification extension would be sufficient to send a notification
does the example project from here Notification Listener (powered by itoox-wrapper) and Itoo work for you?
Also for debugging let me suggest to use the Notifier.LogInfo method (see again my example project) and use logcat to check the log Capturing Device Logs using adb logcat
did you ask for post notification permission?
Taifun