Why my apple watch doesn’t update?

Try the steps here to troubleshoot not being able to update: Update your Apple Watch - Apple Support

Need more help with updating?

Try these steps:

1.    Make sure that your Apple Watch is connecting properly to its charger. 

2.    Restart your Apple Watch.

3.    Restart your paired iPhone.

4.    Try again to update your Apple Watch.

If the update won't start:

1.    Open the Apple Watch app on your iPhone.

2.    Tap General > Software Update.

3.    Delete the update file.

4.    Try again to update your Apple Watch.

Learn what to do if you see 'Cannot Install Update' when updating Apple Watch or if your Apple Watch says you need more available storage to install a watchOS update."