Hi @Anonymous User
The NowTV smart remote that operates the NowTV Stick works over your WiFi network and it could be possible that both Sticks and remotes can become problematic.
If you have already factory reset the Stick by holding the reset button on the Stick for about 15 seconds, then maybe try a different WiFi channel on your Router or if your Router is dual band then try both 2.4ghz and 5ghz frequencies.
Also if you have a HDMI Fly lead adaptor, try that with one of the Sticks to see if it improves the WiFi reception on the Stick when communicating with the NowTV Smart Remote.
I am guessing you have followed these instructions fully ?
What happens when you use the free Roku Remote App with a smartphone or tablet does the Stick work perfectly fine ?