In the event your Sapling Learning calendar events and alerts were accidentally deleted from your device's iOS calendar, tapping Resync in the More section of the app will trigger the app to recreate your events and alerts with the default settings.
Note that resync will remove any custom changes you have made to existing calendar events (e.g., changing the time of an alert), restoring them to the defaults.
If your Sapling Learning calendar events and alerts were accidentally deleted from your device's Google calendar, go into your Google Calendar app, tap the overflow menu (3 dots) and tap Refresh. This will trigger the app to update your events and alerts to their latest version.
You can also purposefully delete items from the Google Calendar web view if they are not working, then try refreshing the calendar the same way.
Note: Updating your notifications from the menu inside the Sapling Learning app will prompt you to apply the changes to New Assignments Only, or All Assignments. Choosing All Assignments will remove any custom changes you have made to existing calendar events.