First, ensure the battery is fully charged, the system is turned on, and the brakes are not engaged when you try to use the pedal assist.
If the pedal assist still does not function, check to see that the pedal sensor near the bottom bracket is still working properly and mounted close to the spinning magnet.
If the problem persists after checking all the above items, contact us for additional troubleshooting, or reach out to your local Schwinn dealer or bike shop.