See if re pairing your remote with the stick works (see link below for instructions).
If no joy, maybe try a full factory reset on the stick, by holding in the small reset button on the stick for about 15 seconds when both the stick and television is switched on.
Also are you using the supplied power adapter that came with the stick and if not maybe try that with the stick instead of using the USB port on your television for power (just to see if the remote control responds after following the above advice).
I know this is an old post but I am having this issue and cannot seem to find a fix or under current circumstances, a way to contact CS. I have done a full factory reset six times over the past 3 days. The remote works for about 15 seconds and then stops. The light stays flashing for a while after and eventually stops. I have resorted to downloading and using the remote app but this really isn't good enough.
I'm having exactly the same issues but I can't factory reset my remote I could only get it to work for a couple of seconds if I took the batteries out and put them back in. I've also downloaded the remote on my phone but it's not the same as having a remote, I'm not buying a new remote for £8 when I got the box for £5 when it was on sale to now TVs customers. The light is still flashing and I've tried pairing them but nothing now, doesn't work at all.