When turned on, no picture, sound or response. LED is OK
I had a similar problem with my HANNSLounge 32", the screen switched on with green light but none of the front panel buttons worked (screen is black apart from showing the input source in the top left).
After powering off numerous times I tried starting up with a blank SD card in the reader and the tv cycled between red green and blue screens and then reset itself. (Some sort of firmware restore?) After which point I had a working screen again! (Will have to see how long it lasts for!)