Why are calendar invites coming through email

I've searched support & found one thing that said to check the box in preferences/advanced, but it was already checked. I used to get all my calendar invites through notifications in my calendar, now they are coming to email. If I press accept on the email it opens it up in safari. I didn't realize I had to then press the download button to get it in my calendar.

BUT WHY? Why the change? My husband & friends still get theirs in their notifications, why did mine change & how do I get it back?

PLEASE HELP!!! 😠