How to fix a black screen on Apple Watch Series 6?

Has the battery of your Apple Watch ever been replaced by Apple?

Depending on the age of your Series 6, the battery might be defective and the watch can not start up anymore.

If the watch does not charge anymore and start up automatically after being put on the charger for longer than 30min, this would be another sign for a defective battery.

You should get the watch either serviced or, given the age of the watch, consider buying a newer model.

If there is more damage to the watch, I would rather buy a newer model.

copied from: Apple Service and Repair for Apple Watch - Apple Support

Welcome and thank you for reaching out. 🤗

According to Apple:

If you connect your Apple Watch to its charging cable and you don't see a lightning bolt on your watch:

• Make sure you're using the Apple Magnetic Charging Cable or USB-C Magnetic Fast Charging Cable that came with your watch.
• Make sure to plug the charging cable all the way into the USB Power Adapter, then plug the adapter all the way into a power outlet.
• Reposition the back of your watch on the charger. When the charger's magnets align correctly with your watch, a lightning bolt should appear on the watch face.
• Make sure that the back of your watch and the magnetic charger are clean. Completely remove any plastic wrap from both sides of the charger. 
• Try a different Apple Watch Magnetic Charging Cable or USB-C Magnetic Fast Charging Cable and a different USB Power Adapter. 
• Leave your watch connected to its charger for a while. If your watch is out of power, you might need to wait up to 30 minutes for the lightning bolt to appear.
• If your watch still won't charge, force it to restart: press and hold both the side button and Digital Crown for at least 10 seconds or until the Apple logo appears.

If you use the Apple Watch Magnetic Charging Dock or the Apple MagSafe Duo Charger with a larger Apple Watch model (44mm, 45mm, or 49mm), you might need to adjust the charger to a different angle or lay it completely flat, to make sure that its magnets align with the magnets in your watch. If you have Apple Watch Ultra or later and it won't connect reliably with these charging devices even when they're lying flat, try removing the watch's band before placing the watch on the charger. If you use a WPT-compliant charger purchased in China or Indonesia with an incompatible Apple Watch, you receive a message: "Unable to charge. This is a country-specific charger. It is incompatible with this Apple Watch." Learn more about WPT-compliant Apple Watch charging.

Learn more:

• Find out what to do if the battery in your Apple Watch drains too quickly.
• If your Apple Watch still isn't working, you might need to get service.

Contact Information:

• United States: 1-800-APLCARE.
• Contact Support.

Additional Support:

• Apple Watch Support.
• Apple Watch User Guide.

Good Luck! 👋🏼😉

Smiliñ 😎 Brian | Community Volunteer