Not really a surprise you can turn off via Amazon Echo and not on, mine does the exact same and i definately would not recomend a smart outlet on a modern Tv, they are designed, like all modern appliances to go to standby, cutting power to them with a smart outlet will stress them undully and shorten component life
My Smartthings Tv app will allow me to change volume, channel and off sometimes and my Samsung connect app gives full control of the Tv inc inbuilt apps, settings and even watch Tv on phone but the same app will not let me switch the Tv on if it has been in standby for an extended period
one thread can be found here but there are many like it