Hey there collettenavarro,
Thanks for reaching out to the Apple Support Communities. We understand you're running into some issues with trying to update your Apple Watch, and we'd be happy to help.
To get started, when you say that the battery is at 100% and connected to the charger, are you referring to the iPhone or Apple Watch? We ask because you would want to ensure that your Apple Watch is connected and charging if it's not.
If it is, give the steps listed in the following resource a try under the "If you need help updating" section: Update your Apple Watch - Apple Support
Keep us updated on the results.
Cheers!