What it means — Apple
If a red lightning bolt appears on your Apple Watch screen, it means your watch doesn't have enough battery power to turn on. When you connect your watch to its charging cable, the red lightning bolt changes to a red lightning bolt inside a ring.
What to do — Apple
- 1 If your screen stays blank even when you press the side button, or if the charging cable icon appears, you might need to charge your watch for up to 30 minutes before it will turn on.
Read the full article for pictures and model-specific details: If your Apple Watch won't turn on or won't charge ↗