Since the water frequently 'travels' from the point of entry to the place where it shows on the ceiling, poking a hole in the ceiling is not usually much help in finding the leak.
If the rain collars are all new and properly installed, have you checked your flashing at the chimney and are your gutters properly attached and flowing freely? Does the roofing have a proper drip edge at the eaves and gable ends or is there an opportunity for 'run-back'?

Thanks, I drilled a hole then inserted a coat hanger so I could see. That marked the general area of the leak it turns out. The wood had splintered and left a hole under the shingles. Impossible to see from topside. My roofer put a piece of wood though it to mark it.
After putting metal flashing and replacing a shingle the hole is now fixed. Some insulation is wet, do I need to replace it or let it dry? I pulled it up and out of the way. It is way too hot to go back up in the attic.

If the leak is fixed, rolling back the insulation may permit it to dry, as long as you have proper ventilation in the attic, though it may take a while longer for the ceiling board.
I'd take a wait-and-see tact, first making sure that it is just damp and there's not a wetter area, also.
You may end up with a water stain on the ceiling that will have to be primed and painted, or further repaired if it is distorted.