1. Please check whether the mode of the S3+ is correct.
When the battery is installed, the green light flashes to indicate that it is in speed mode. If the mode does not correspond to speed, the data will be abnormal.
If the sensor is connected to a bike computer, please make sure the mode of the sensor is correct, then forget the sensor on the bike computer, and connect again.
2. Maybe a compatibility issue.
Please try to connect the sensor to Magene Utility APP, then see if the speed data will display.