I have same issue. Just started in last day or two. Worked fine the previous 2 weeks.
That's the message, that the Q60T43 has to be connected to the same wifi network as the iPhone. And, of course, it is. I've verified both through their respective SETTINGS. Still Smart Things doesn't see the TV even when only a couple feet away. I deleted the Smart Things from the iPhone and re-installed. No change.
Somewhere (I thought in the response to this post) I was given a phone number for the Smart Things team who could help with this problem. I called them. Turns out, they can only help with Smartthings Lifestyle. The Smart Things app I'm talking about is the one by TV Cast. Both apps are named Smart Things. Very confusing. Anybody have info about the one from TV Cast? Why it no longer works?