"The creator of this list has upgraded these reminders." on iPhone, even though the phone is running version 17.1

I had the same problem for almost a year except was 'busy' and didn't get around to fixing it till a couple days ago. I found on another website m#cr#mours to "sign out" of iCloud on the affected device, then sign back in.

Fixed it for me though the process of 'signing out' of iCloud takes a leap of faith as it asked me to save or delete photos and messages on my M1 MacBook Pro when signing out. I chose to save and take the chance that it might duplicate files 'Sometimes the Remedy Is Worse Than the Disease?' but got lucky and problem fixed, no issues.

Wish that was the fix in my case, but I’ve tried signing out and signing back in several times, to no avail.

Did you find a fix to this problem?