Not all fans can be controlled by PWM.

Try your fan directly with 5V power supply, and see if it runs.
Most likely, it won't run at 5V.
Increase the voltage and see at what voltage it will start running.

If it starts running at around say 10V ~ 11V, then you will have to change your fan, which most probably is controlled by an internal electronic controller.

Try your circuit with a simple traditional DC brushed motor and see if your PWM works.