You're arguing for the existence of a soul, for dualism. Nothing wrong with that, except we have never been able to measure it, and have never had to use it to explain any phenomenon of the brain's working. The brain follows the rules of physics, like any other objects of the material world.

A pen and paper simulation of a brain would also be "a thing happening" as you put it. You have to explain what is the magical ingredient that makes the brain's computations impossible to replicate.

You could connect your brain simulation to an actual body, and you'd be unable to tell the difference with a regular human, unless you crack it open.