TX9 Pro , 6k , Android Box

Hi

My TX9 Pro, 6K, Android Box is somehow stuck,after i switch on the Box it shows the TX9 Pro theme and thereafter the screen just goes blank.

The box is still on though, i have tried resetting using the button in the AUX port with no luck, how does one go about RESETTing the box if you can see nothing on the screen?