Installed app and now remote not working

I installed Mediahh apk on to my Amazon Fire TV stick. I then restarted the stick and opened the app using the remote. Having watched a couple of vides I decided the app wasn't what I wanted so I used the remote to exit the app. Suddenly the remot stopped working. I've changed the batteries and it's not working. I have used the remote control app on my phone to uninstall Mediahh and also restarted. I've tried to pair the remo but the stick doesnt detect it. I have read other threadds about restarting the stick (which worked for other people) or unpairing but I cannot find the option to unpair it.
I used adbFire to install the apk.
Does anyone have any advice what to try next?
Thankyou