Recovering Reminders without an archive on iCloud
How can I recover Reminders if there is no archive to recover from?
[Re-Titled by Moderator]
Original Title: Reminder Recovery
MacBook Air 13″, macOS 14.7
If you don't haven't synced them to iCloud or backed them up, they are gone.
Restore your reminders on iCloud.com - Apple Support
Did you possibly recently remove an email account from your Mac? If so, add it back and see if they Reminders are restored.