Can not update 8.7.1 for apple watch series 3

Hey there BenHuynh1,

Thanks for reaching out to Apple Support Communities. We're happy to provide some assistance.

The steps under the "If you need help updating" section of this article may help resolve issues updating your Watch:

Update your Apple Watch - Apple Support

1. Make sure that your Apple Watch connects to its charger. 

2. Restart your Apple Watch. Press and hold the side button until you see Power Off, then drag the slider. To turn your watch on again, press and hold the side button.

3. Restart your paired iPhone.

4. Try to start the update again. 

If the update won't start, open the Watch app on your iPhone, tap General > Usage > Software Update, then delete the update file. After you delete the file, try to download and install watchOS again.

Learn what to do if you see 'Cannot Install Update' when updating Apple Watch.

If the issue persists, reach out to Apple directly to investigate:

Get Support

Have a great day!

Welcome back BenHuynh1,

We recommend you use the previously provided link to contact Apple Support directly.

Cheers.