So I have YouTube TV and it has been working perfectly on my Shield. However I got another Shield and when I open YTTV i have a problem. The app won’t open, what shows up is the page from the App Store and then I have to hit OPEN to use the app. I uninstalled and tried again and still had the problem. Works normally on my other one though. Both have the updated system.
Do a factory reset of your Shield and then install.