If your Apple Watch is not charging on the USB-C Fast Charging Cable for Apple Watch (ST-QCAWM), the usual causes are a power source that supplies too little wattage, the watch not sitting squarely on the magnetic charging head, or debris between the two. The USB-C Fast Charging Cable for Apple Watch needs a USB-C charger or port that provides 5W or more, and it outputs a maximum of 5W.

How to fix charging problems with the USB-C Fast Charging Cable for Apple Watch

1. Connect the cable to a USB-C charger or port that provides 5W of output or more. A very low power port will not start a charge.
2. Place your Apple Watch on the magnetic charging head and look for the charging indicator animation on the watch screen. No animation means the watch is not picking up power.
3. Reposition the watch so it sits flat and centered on the magnetic head, then let the magnets pull it into place.
4. Clean the back of your Apple Watch and the charging head. Dust or grit between the two surfaces stops the charge.
5. Try a different USB-C port or power source, such as a wall charger instead of a laptop port.
6. Try a different wall outlet.
7. Check that your USB-C power bank supplies enough wattage if you are charging on the go. The cable works with USB-C power banks, but a low output bank will charge slowly or not at all.
8. Test the cable with a different Apple Watch, or your Apple Watch on a different charger, to work out whether the issue is the cable or the watch.
9. Confirm what you are charging. This cable is only compatible with Apple Watch and will not charge Samsung, Garmin, or other non-Apple smartwatches, and it does not transfer data.
10. Set the right expectation on fast charging. Fast charging works with Apple Watch Series 7 and later and Apple Watch Ultra and later. Apple Watch SE models still charge, just not at the faster rate.
11. If you are charging AirPods, use a supported model. The cable works with AirPods 3rd generation that have a MagSafe charging case and with AirPods Pro 2nd generation, at regular charging speed rather than fast charging. The AirPods Pro 2nd generation case has a built-in magnet and snaps into place, while the AirPods 3rd generation MagSafe case does not magnetize, so rest it on top of the charger on a flat, level surface.