Apple Watch Series 8 will not charge

The checks in more detail

to plug the charger into a wall adapter and not a computer, and then to force restart by holding the side button and Digital Crown for ten seconds. The Series 8 has a temperature sensor and sleep tracking that can use the battery overnight, and the watch charges to a limit when Optimized Battery Charging is on, holding at eighty percent until you wake, which looks like a fault. A red lightning bolt means very low charge. If it does not charge on a second charger, Apple should look at it. The watch's charging screen shows percentage and a green lightning bolt, and the screen goes dark after a while to save power;

tap the screen or turn the Digital Crown to wake it. A watch that appears dead on the charger may simply have turned off the display. Check by pressing the side button, and wait for the percentage to appear before concluding there is a fault. Another point for the Series 8 is that the charger puck must sit on the back of the watch with its cable straight, because a bent cable can lift one edge of the magnet away. Fast charging on the Series 8 uses a USB-C cable and a 20 W adapter, so a slow charge on an old five-watt block is expected and not a fault.

If the watch charges but still empties during the day, check Battery Health in Settings, Battery on the watch, since a capacity below about eighty percent after a few years is normal aging and may justify a battery service. Some people place the watch on a charger stand that tilts the screen, and a case on the watch that is thick can reduce the contact with the magnetic puck. Take the watch out of the case when charging, and check that the puck's center aligns with the watch's back. If the watch charges only at an angle, replace the puck, which wears like any cable. A new genuine cable is inexpensive.