Apple watch series 2 watchOS3.1

I'm trying to reset my Apple watch series 2 with watchOS3.1. It was paired with my iPhone 6 which was factory reset after the screen change. I could not restore the backup so the watch is no longer paired with the phone and I don't have the passcode anymore. I have removed it from my account and was trying to reset the watch with the various methods I found in the forum and on the Internet, ie. pressing the power off slider (while on charger as described) does not bring up the "erase all content" window. The screen keeps showing "Wrong passcode Open the Apple watch app on your iPhone...." Are there any other ways to simply factory reset the watch to be used again?

Many thanks.