1. pairing problem: please make sure that your iWatch is properly paired and connected. Check the pairing guide to make sure you have followed the correct steps.
2. Activation problem: Please make sure that your iWatch has enabled sports and fitness functions. In the "Fitness" application of iWatch, you can choose to activate various sports types, including cycling.
3. Sensor problem: If your iWatch is equipped with a GPS sensor, please make sure that you wear the iWatch on your arm when riding, so that the GPS sensor can accurately record your motion trajectory.
4. Network problem: If your iWatch needs to connect to the Internet to record your sports data, please ensure that your device is connected to an available Wi-Fi network or mobile data network.
If none of the above steps solve the problem, please try to restart iWatch and make sure that your device has been updated to the latest software version. If the problem persists, I suggest you contact Apple technical support for more help.