Apple Watch Ultra is not asking for passcode after factory reset

Hi All,

I had to reset my Apple Watch. I did a factory reset and paired it again with the same phone. I set the passcode, but while using the watch, it does not ask for the passcode. I checked the passcode settings, and it has been disabled.

I removed the watch from my iCloud, deleted the watch software, and added and removed it several times, but no luck.

Then, I paired my watch with another iPhone, and the passcode worked fine. I unpaired it and paired it again with the original phone, and the passcode did not work again.

What's the mystery behind this, and how can I fix it?

I would appreciate your quick help.

Regards,

RR

[Re-Titled by Moderator]