I am having the same issue on my new Smart TV. I have reset the Samsung Hub (which was annoying because I had to sign onto every app again and even reinstall some). I have also reset my modem and the network settings on my TV.
Any update/resolution on this issue? I'm having a similar issue with my q90T. The Samsung Health app no longer loads. When I select the app it says "loading Samsung Health", however, nothing happens. I do not get an error message...there's just the blue screen. And the TV thinks the app is open because when I back out, I get the 'Exit Samsung Health' pop-up box asking 'Are you sure you want to exit'.
So I realized that I didn't check the Samsung Health app on my other tv. When I checked the other tv the app worked just fine. Having read someone else mention that they uninstall and reinstall the app I thought I'd try that. Before I uninstalled, though, I figured I better make sure the app was still accessible in the Apps menu. The Samsung Health app was there listed under Downloaded Apps. I clicked on it and an Information box popped up saying a new version is available, would I like to update now. I took the update, then opened the Samsung Health app and wouldn't you know it worked just fine. So try going into the Apps menu on your tv and see if your Samsung Health app needs updating. Good luck.