To troubleshoot issues with notifications for birthdays or events in your Apple Calendar, follow these steps:
1. Check Calendar Notifications Settings: Enable notifications for the Calendar app, configure alert settings, and turn on sounds for auditory notifications.
2. Open the Calendar app and check the calendars you want notifications for, including birthdays.
3. Verify event and birthday alerts: Check if alerts are set up correctly, and ensure Do Not Disturb mode isn't blocking notifications.
4. Check Calendar Sync Settings: Ensure Calendar is synchronized correctly, fetch new data, and push it at a suitable interval.
5. Restart your iPhone, update iOS, reset all settings, check for Calendar app updates, and contact Apple Support if necessary.