Calendar event from an email invite doesn't go to iCloud, and I can't invite anyone
I got a calendar invite from a dog groomer after I booked an appointment. Their website sent me an .ics file that I opened in my Calendar app.
The event is in my Home calendar, but I can't add people to it, nor can I see it on my iCloud calendar on the web. The "Add People" option in all other calendar events, doesn't appear in this event.
I tried swapping it to different calendars, I tried copying and pasting the event into the calendar again, I tried "duplicate" from the drop down on the event. No dice.
MacBook Pro (2021)