This has happened to me too. Longest time I went without seeing a camper was like 3 and half weeks.
You may just be getting extremely unlucky, or it's possible that when a villager is about to move in(when you plot reset), that nobody will be in the campsite.
Yeah I thought campers were a weekly thing in this game, but then I proved to be wrong. I am generally very unlucky with campers, only get one maybe every 2 or 3 weeks. However, I heard that some people got campers every day of the week. So yeah it's a luck based thing, you just have to keep on checking every day It's not a glitch, that is for sure.