#dming help

I've been playing ttrpgs for a while, and I've never had this really come up but - what do you do if a player misses sessions consecutively? Or cancels 10 minutes before a session is about to begin?

It's happened to my current pathfinder campaign for four-ish sessions in a row; the same player cancels or calls out anywhere from a day to ten minutes beforehand. Some of the reasons are absolutely valid, but the fact that it's building - and we haven't really been able to get a session in recently - is frustrating. They're a friend-of-a-friend of one of my other players, and they're genuinely pretty nice, so I don't want to kick them out, but I don't really know the etiquette of what to do. Do I warn them? Do I just keep cancelling and doing one-shots with the players that do show up? Do we just scrap the campaign? Do I kick them out?

Any help would be appreciated !! Thank u!!! For some background, I have been playing D&D for almost a year and have been DMing for a while aswell, but mostly on oneshots with pre-made stories, places and NPCs. This time I'm creating an original oneshot from zero.

Since these questions need some discussion, please feel free to talk to me in dms. It would be equally appreciated!

How do I make a scene immersive? My initial plan is using all my brainpower to make my favorite kind of description. For example, in order to describe how damn hot the one confined space they are going to be in, im gonna be saying "you can feel hundreds of tiny flies fly under your clothes, forming a blanket of heat that sticks onto your skin and slowly asphyxiates it." (its the best way i can describe being woken up by the heat on a summer night, dammit Greece). Is it too much? Should I just say "The small, confined cellar does not allow any chillness of the outside air to reach you, and you therefore feel very hot." ?