aCalendar is not involved in calendar synchronization. The app is just an user interface to the Android calendar storage and does not save any calendar data itself.
Hint: The google calendar app does not use the Android calendar storage for their own data, that's why google calendar data might be shown in the google calendar app, but not in aCalendar.
Please make sure that this is not your issue: Events from one or more calendars missing (wrong profile selected)
If that's not the case und you experience problems with Google Calendar sync please check following:
- Please make sure to have the latest Google Calendar app installed from Google Play. (Early versions of Android included a Google Calendar sync adapter, but this was moved to the Google Calendar app, to be able to update via Google Play.)
- Test if synchronization works when you open the Google Calendar app. If it's working (the Google Calendar app synchronizes only in the foreground) this is a clear sign for background data/process limitations in Android.
The setting to turn on background data for the Google Calendar is different for Android versions and manufacturers. Mostly it is in the device settings under 'Data Usage' or in the 'app info' for the Google Calendar app (Usually just long press on the Google Calendar app icon in order to open the 'app info'). - If (background) data is switched on for the Google Calendar app and sync is still not working, please check your:
- Google account settings under (this may vary!) device settings / accounts / Your google account / account synchronization / calendar
- energy saving options
- global sync settings in Android
Please see also: General Sync Issues / Sync of two devices