I advice you to Why won't my television power on. It is not the same model as yours but most of them seem to work the same.
To recap some of the key points form that post and general advice:
- unplug everything including the power cord. Wait a minute and plug the power cord in and try if the tv works.
- If it doesn’t work see if you have warranty from Hisense or the store you bought it from. Even if you do not have warranty you can contact Hisense customer service and ask if they have a solution.
- If that doens’t work you’ll have to find a solution yourself. It seems most likely to be a power source problem or backlight. This means taking your tv apart and finding out if you can repair it.
Of course you can always come back here with additional questions on repair if that’s what you end up doing yourself.