First make sure you are connected to primary hdmi port (hdmi0 - the one closest to power connection).
Next, disconnect TV from mains for several minutes.
Remove all HDMI connections, and just connect one HDMI from TV to Pi (no AVR etc).
Power on TV first, set to Pi's AV input, then power on Pi 4.
Does CEC remote work? If so you can try connecting the other hdmi devices..
Perfect 
Thank you 