Have rad rover and had same issue.  Just rode with throttle and no pedal assist for months. Recently contacted Rad through their email and got fast results. A tech spoke with my husband ,diagnosed the problem of missing magnets. Still under warranty so they shipped the part. Now through utube video we see we need a crank puller tool to do this job ourselves.  Will need to order this tool online. Plenty of videos to show you how to do this job. We aren't near a bike shop.