Please try the following to resolve your Google Classroom > Google Calendar sync issues:
Make sure Calendar sync is turned on
- Open the Settings app on your device (not the Google settings app).
- Tap Accounts.
- Select an account.
- Tap Account sync.
- Make sure Account sync is turned on for Google Calendar.
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Confirm that the correct calendar is synced
- Open the Google Calendar app .
- In the top left, tap Menu .
- Tap Settings .
- Tap the name of the calendar that isn't showing up. If you don't see the calendar listed, tap Show more.
- At the top of the page, make sure Sync is on (blue). You'll only see the Sync setting for calendars you've created, but not your primary calendar (this is usually called "Events" unless you've changed its name).
Note: It might take some time for your events to show up after you turn on sync.
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Manually sync your Calendar
- Open the Google Calendar app .
- In the top right, tap More Refresh.
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Make sure Calendar storage is turned on
- Open the Settings app on your device (not the "Google Settings" app).
- Tap Apps or Apps & notifications App info.
- In the top right, tap More Show system Calendar storage.
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Check your device's storage
Calendar stops syncing if your device is running out of storage.
- Open the Settings app on your device (not the "Google Settings" app).
- Find the Storage section.
- If you need to clear space, try uninstalling apps you don't use or deleting files or photos from your device.