If you see "Unable to install update" when trying to update Apple Watch Series 1 or Series 2
Try these steps if you see an error that says "Unable to install update" when updating your Series 1 or Series 2 Apple Watch.
Before you begin
Learn which Apple Watch model you have if you're not sure.
Update your iPhone to the latest version of iOS.
Make sure that your Apple Watch is on its charger and charged at least 50 percent.
Connect your iPhone to Wi-Fi.
Keep your iPhone near your Apple Watch as you go through these steps.
How to fix the "Unable to install update" error
Try these steps. If one doesn't work, move to the next one.
Turn off Unlock with iPhone
Open the Apple Watch app on your iPhone, then tap the My Watch tab.
Tap Passcode, then turn off Unlock with iPhone.
Tap the My Watch tab again, then go to General > Software Update.
Try to install the update again.
Turn off Bluetooth and Wi-Fi on your iPhone, then update directly from your watch
On your iPhone, open the Settings app, tap Wi-Fi, then turn off Wi-Fi.
Go back to the main Settings screen, tap Bluetooth, then turn off Bluetooth.
On your Apple Watch, open the Settings app, then tap General > Software Update.
Try to install the update again.
Let your Apple Watch update automatically overnight
Open the Apple Watch app on your iPhone, then tap the My Watch tab.
Tap General > Software Update > Automatic Updates.
Turn on Automatic Updates.
Make sure that your Apple Watch is on its charger and in range of your iPhone that's connected to Wi-Fi.
Let your Apple Watch update overnight.
Contact Apple Support
If you continue to see the error after trying the steps above, contact Apple Support.