We are aware of a problems recently affecting the 5 app on some LG televisions where an activation code isn't being generated on the sign-in page or users were having problems playing content when accessing the app.
We believe that this issue should now be resolved and you should be able to access and play content on the app again.
If you are still experiencing problems, please try turning your television off, unplugging it and leaving it for a few minutes before turning it off and that will hopefully clear the problem.