Are you using the hdmi port next to the power jack on the RP4 ?
Did you try toggling the Source button on the Soundbar ?
Did you trying turning each component off and then on once connected ?
Thanks for the reply. I have ensured it was in the correct HDMI port of the RP4. It does work just fine connected to the TV, just not on the soundbar. I've toggled the source on the soundbar and cycled through the HDMI ports on it and nothing displays. It does display my PS4 fine though, so I do know it's passing that just fine. I have also tried cycling the power too.