First thing, eye ball the old parts and the new parts and make sure they are the same.
Assuming that you have the correct replacement parts, then I would check the direction of the free wheel of the new nylon gear (to rule out factory defect).
Review 0.41 part of the above video. With the shaft placed in the nylon gear, it should bite when the nylon is turned clockwise and freewheels when the nylon is turned counter clockwise. And not the other way around.
If you open the cover at the chain ring side, the gear and pinion should be meshing together. The small pinion should be spinning when the motor is on. If not, then the inside rotor with it's attached pinion is not making contact to the nylon gear.
Addendum:
Count the number of teeth for the new parts and make sure they are the same.