I wasted the equivalent of an entire day reading these discussions and others, trying to solve this problem. I did everything - all the keychain stuff; I rebooted my Mac, iPhone, watch, updated all software. I tried every nuanced option within these and many more protocols. Nothing worked. Why? No clue.
Finally punted and simply unpaired my watch. Once I paired up again (you know, when your watch gets that blue, fuzzy outer space thing that looks exactly like the Robot's face on the new Lost in Space series) and it immediately asked me if I wanted to update now or wait till later.
Update now! Boom. Solved.
Note: I've been an Apple fan/advocate/ambassador since I learned on a MacPlus in the late 80's. I've been through every era, every upgrade, every OS, almost every desktop, laptop, wireless keyboards, routers, monitors... every device including the iPad Pro HUGE fan.
But is it me or has something has gone terribly wrong inside Apple? "Help! Steve!" :)
Regardless, after 33 years, I'm still here and will never abandon the brand. I've earned a lifetime worth of income using Apple's tools. I just want them to get their **** together. :)
🖤