First and foremost, make sure you're using the supplied power adapter and not the TV's USB port. It appears the cheapest Express model may no longer come with a power adapter, so if you didn't get one make sure the power adapter you're using can supply at least 1 Amp. Forget anything about your WI-FI and even HDMI related stuff. If it doesn't get past the startup animation and pressing and holding the reset button for 30 seconds with the power connected didn't help then it's either a faulty device or an insufficient power source.
If you just purchased it you should be able to take it back to where you got it. If not: