SmartThing app in new IOS 1.6.35 (iphone) cannot rename devices connected to Samsung Connect Home. After you apply the renaming, the spinning progress icon will keep on spinning.
Try signing out of the app and logging back in.
I’ve been having the same issue, among others, but it’s really been irritating. Logging out and logging back in doesn’t fix anything. I even went to the extreme of factory wiping my device and starting all over!
NOTHING has fixed the issue.