A couple of things that you could try, and i am guessing you are using a NowTV box.
Try a reboot on the box by unplugging the power for say a minute, then switch the box on again.
Make sure the light is shown on the box when the power is on, if there is no light check the power cable at both ends.
You could also try a forced update to see if that works, press the following keys in this order on the remote controller 5 x Home, 3 x FF, 2 x RW.
With the TV and box switched off try disconnecting and reconnecting the HDMI cable, if that doesn't work try a different HDMI port on the TV, if that doesn't work try a different high speed HDMI cable.
Last resort try a factory reset by pushing a pin for 30 sec in the small reset hole at the rear of the box (If you own the new 2016 smart box the reset button is underneath the bottom of the box) before undertaking a factory reset make sure that you know your wifi password and nowtv username & password.
My box has done the same flashing light on the front, won't power up and nothing on the TV the box for the past 3 or so weeks has been doing some wired stuff 3 times the menu options have gone over night so you can get TV and have to reset now not booting up if the above fails how I assume the box is faulty how do I or where do I go to get the box repaired or swapped less than a year old