Watch is constantly showing update failed Cancel or open app
Unable to update
Apple Watch Series 1, watchOS 6
Question marked as
Top-ranking reply
Try installing the update from your iPhone next time, using the Watch app. Make sure both the Watch are connected to the network and you are signed in to iCloud as well.
If the download is stuck, check that there is no passcode prompt pending on the watch at that time.
Hopefully that helps?