Hi yes put the sub next to the tv.
Red flashing light sounds like optical – I’ll download the soundbar manual to.
I’ve changed to cinema day and changed the Firestick up to 12 bit. Also changed audio setting to be Dolby plus. The sound bar is attached via audio out, the one with the little red light.
Is this previously or today?
12 bit depth – YCbCr colour format on firestick – check that. Though you can scroll through all settings, but you’ll have to reboot the firestick if you change any setings.