Just worked it out.. I had to go into the apps manager and I couldn’t delete the Apple TV app, but I could re-install and that worked for me.
for me that was found in
settings (top right cog)
find the Apple TV app, an reinstall
so we're now months and months on from Apple TV launching. The app is pretty much available on every platform, even on the ps4 which is much older than my TV. YET still Samsung will not offer it in the App Store. IT's just ridiculous. Whoever is making this devision is grossly incorrect to think any customer will upgrade a perfectly good TV just for an APP. One can only assume this is the driver.