Got I working. All I had to do was switch AVR to TV output from e/ARC to regular 2.2 HDCP and it's all savvy!!Finally sat down with the replacement FireStick, problem yet again:
1 -Works when I connect it to my TV
2 - Doesn't when it is connected to the AVR Denon X2300W - All ports are HDCP 2.2 (assignable); do I need to change any setting here before it will be detected?
Any help greatly appreciated. If you need me to post my AVR settings here, I can.
Wonder why it happened though!