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I was getting the verification failed message after putting my son’s iPad passcode in, the solution that worked for me was to change the passcode on his iPad, then use the new passcode when it wanted me to enter the passcode on the iPad.

it worked, I was able to get the watch up and running, then I changed the passcode on the iPad back when I was done.

good luck!
 
I was getting the verification failed message after putting my son’s iPad passcode in, the solution that worked for me was to change the passcode on his iPad, then use the new passcode when it wanted me to enter the passcode on the iPad.

it worked, I was able to get the watch up and running, then I changed the passcode on the iPad back when I was done.

good luck!
Hadn't tried this yet either--going to do it now and see if that helps!

EDIT: Oh my god this worked, you glorious person. Thank you!
 
I spoke to a tier 3 Apple support and he stated that when the watch requests my kid’s MacBookPro password it is requesting the computer’s admin password. He said that if the verification fails we need to wait 8 hours and try again. So far I’ve tried everything that has been suggested here and nothing has worked. I’ll try again tonight and provide and update later.
 
I was getting the verification failed message after putting my son’s iPad passcode in, the solution that worked for me was to change the passcode on his iPad, then use the new passcode when it wanted me to enter the passcode on the iPad.

it worked, I was able to get the watch up and running, then I changed the passcode on the iPad back when I was done.

good luck!
I tried changing the passcode on my son’s iPad, but that didn’t work. I called Apple support and they had me reset all settings. resetting all settings deleted the passcode and turned off (disabled) passcode. Then, I activated passcode and set a new one (same as the old one). That did the trick. I guess the devil in the detail is the difference between the words “change” and “reset”. The first time around I changed, not reset.
 
I wanted to provide an update for those of you who are still stuck, this is what worked for me.
I was getting the verification failed message after putting my son’s iPad passcode in, the solution that worked for me was to change the passcode on his iPad, then use the new passcode when it wanted me to enter the passcode on the iPad.

it worked, I was able to get the watch up and running, then I changed the passcode on the iPad back when I was done.

good luck!
On my case, I simply turned off passcode and when I turned it on I was prompted to create a new one and also enter the password to unlock my son's MBP which was to be used to authenticate any new devices with his iCloud (such as a new watch!) but this too failed.

Based on my previous conversation with the tier 3 Apple rep, I then turned on keychain on his iCloud via his MBP.
I restarted both his MBP and iPad and try to re-enable passcode again. This time it worked!

Then tried pairing the watch again and provided my son's MBP password during authentication and it worked right away. I hope this help people who are stuck in a similar situation.
 
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