Welcome to the forum. Not sure which type of reset you did, but try a hard reset of the box by pushing a pin into the hole at the back and holding in until you see the box restart (or if it's the larger smart box hold the reset button underneath until it restarts).
Then when you are in the lets get started screen hold the remote close and direct to the box and press OK, if you see the light flash on the front it's probably not the remote at fault. If you don't get any further after a few hard resets it could be the box to blame. If the competition was by NOW TV contact them on live chat or send a message and they should be able to arrange a replacement. Otherwise get in touch with the competition organisers.
You can send the NOW TV Team a message or get to live chat from the Contact Us page