This may be a slower time of the year in terms of carp fishing as they are just recovering from all the sex haha. That said though some would still feed and especially since others around you were catching you know you could get them.
If your hair rig is set up properly, you shouldn't need to set the hook. The idea of the hair rig is for the fish to hook itself, the moment you lift your rod up and lean into the fish should be all it takes to bury the hook in. If you saw your rod tip tapping, that's very good sign. Either the fish was swimming around your bait pile feeding, and bumping into your line, or they were actually mouthing your hookbait but spitting it back out. (if you watch some underwater videos you'll see that this happens alot, with the perfect hair rig set up fish would still manage to mouth it and not get hooked, there are other rigs/methods of fishing that may increase hooking % but that's another debate). Be patient when you see the bumps, eventually they'll get to your hookbait.
Keep at it. You will get one. I don't even remember how many times I have skunked until I got my first one. Even now I still have my fair share of skunking days
Do let us know when you get your first!