Missing reminders on iPhone

Restore your reminders on iCloud.com

1. If you do not have shared reminder lists, go to the next step. ... 
2. On iCloud.com, click. ... 
3. Click Restore Calendars and Reminders. ... 
4. To the right of the version you want to restore, click Restore.

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Restore your reminders on iCloud.com - Apple Support (IN)

If your Reminders were not stored on iCloud but on other email Accounts. Please see the pic below and add the account in the iOS mail app

Step-by-Step Guide to Restoring Your Reminders

• Assess Shared Reminder Lists (If Applicable):
  • If you have shared reminder lists, take note of which lists you’re sharing, whom you invited to share each one, and their permission levels (view and edit or view only).
  • Also, record any reminder lists others are sharing with you.
• Access iCloud.com:
  • Open your web browser and navigate to iCloud.com.
  • Sign in with your Apple ID and password.
• Navigate to Data Recovery:
  • Click the “App Launcher” button located in the toolbar.
  • Select “Data Recovery” from the options.
• Choose Restore Calendars and Reminders:
  • You’ll see a list of available versions, sorted by the date and time they were archived.
  • Locate the version you wish to restore and click “Restore” next to it.
  • Note: If there are more versions than displayed, scroll to view them all.
• Wait for the Restoration Process:
  • It’s crucial to wait until iCloud finishes restoring your reminder lists before making any changes. During this process, any modifications you make will not be saved.
• Reshare Shared Reminder Lists (If Necessary):
  • If you had shared reminder lists, you’ll need to reshare them and ask others to re-invite you to share their reminder lists and calendars. Follow the steps to share a reminder list on iCloud.com.
• Enjoy Restored Reminders on All Devices:
  • Once the restoration is complete, your reminders and reminder lists will reappear on all your devices with Reminders turned on in iCloud settings.