How to fix Apple Watch when red sign come out?

Hi

If your Apple Watch is displaying a red exclamation mark, then you will need to contact Apple Support (mail-in service may be available, if required), make a Genius Bar reservation or visit an Apple Authorised Service Provider to arrange for your Apple Watch to be serviced:

• Contact - Official Apple Support
• https://twitter.com/applesupport
• http://www.apple.com/retail/geniusbar/
• https://locate.apple.com/

More information:

Get help if your Apple Watch displays a red "!" - Apple Support

If you Apple Watch has displayed a temperature warning sign, then follow the instructions here:

Keep Apple Watch within acceptable operating temperatures - Apple Support

If it will not turn on after being allowed to cool down, then follow the instructions here, including contacting Apple Support (mail-in service may be available, if required), making a Genius Bar reservation or visiting an Apple Authorised Service Provider if necessary:

If your Apple Watch won't charge or it won't turn on - Apple Support