I have a NOW TV 'black' (4200SK - Roku 3) and it's frozen on me. Last night when I was watching it said it was going to close and was trying to use my remote to stop it but turned off. Today while trying to use it, it's none responsive. I've change the batteries and there's nothing wrong with the controller.
Have you tried a soft reboot on the nowtv box and your router by unplugging the power for 30 secs ?
If that doesn't make any difference, then see if you can access the hidden menu on the box by pressing the Home Button 5 times, then quickly press the FF button 3 times, then quickly press the RW button 2 times on the remote controller.
Update the software, even if you are on the same version number.
If the remote doesn't respond or work to the above, then maybe download the free Roku remote controller App onto your smart phone from the phone Apps Store and then try a forced software update on the box again.