Unfortunately, the old Samsung TV app does not support Live TV and has known issues with 10 compatibility.
The good news is we have just released a new app for TV's 2018 and newer which includes features such as Live TV.
If you have a model newer than 2018 and cannot see the new app, please submit a ticket and include the TV model number and year it was purchased.
If you have a model newer than 2018 and are still experiencing problems, please submit a ticket with information on what the issue is, and a screenshot of the 'App Info' screen so we can investigate: How to find the App Info screen on a Smart TV
If you have a model older than 2018 it is recommended you use Chromecast or Airplay to get the most out of your 10 experience.