If your pedal assist on your electric bike isn't kicking in there is a good chance your cadence sensor just needs to be adjusted a little bit.
If you look on the crank of your bicycle, on the right side where the chain rings are, there is a small black wheel with 12 magnets in it around the edge. Behind that magnet wheel, closer to the frame of the bike, is a small sensor that reads the magnets to tell the motor when the pedals are turning.
To adjust this sensor, just slide the magnet wheel closer to the sensor, making sure it's even on all sides.
Crank does need to be taken off to replace the Cadence Sensor.
If your sensor is working correctly you should be able to see a red light flashing on the back of it every time a magnet passes.