Apple Calendar Email Alerts not working: "You must add your own card and email address in Contacts to be able to use mail alerts."

FINALLY!!! Solved! Does this solution work for you?

STEP 1: Go to Users and Groups in System Preferences

STEP 2: Click "Contact Card: Open..." button

STEP 3: Your Contacts app will open - It will open a contact card with your Username

STEP 4: Add your email to the contact card.

Presto! Emails alerts should work

Note: If in STEP 3 if there is no contact card with your Username, create one, add your email. Ensure you delete any duplicate contact cards with your Username.

Good Luck!