Apple Watch Series 9 won't update to watchOS 10

Hi Dogcrazy25,

Thanks for posting in Apple Support Communities.

There are few steps you can take to ensure Apple Watch completes the update.

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.

Update your Apple Watch - Apple Support

Regards.

Be Patient, it has a lot of thinking to do. The Preparing stage can be slow, depending on the size of the update even 1 hour is possible. Just be patient, and id updating your Apple Watch remember you MUST have the watch powered externally on its charger for the install to complete.