This seems to be a problem which arose for some last year. It has now hit my account. The app doesn't load - I just get the "Well, that didn't go to plan... NOW Tv isn't loading. Please try again in a bit." message.
Really annoying. Going to the content store and launching from there did work, but now it doesn't. There was a recent WebOS update - has that caused the problem? LG please sort this out.