"The Harkles had to turn down the invitation to the mayor's glitzy party?" That may be Harklespeak for "they weren't invited." Why would they be considered as highly important in the film industry when they've done zip for Netflix? I can't see Netflix wanting the Harkles involved.
The mayor, more than likely declined the Harkles invitation to Casa del Sussex to avoid the Netflix film crew. I agree with Karen, the mayor is not a close friend, perhaps not even a "close acquaintance.

"The Sussexes are said to have welcomed cameras into their mansion for a reality-type series that could be in the mould of The Osbournes - although it is not yet known if the couple's two children, three-year-old Archie and 11-month-old Lilibet, will also feature."
I find this a hoot, The Osbournes were the original "reality show" not a docuseries. So it sounds like the project is, "The Harkles At Home", the reality show.