Ok.
One other thing you can try without additional cost;
Make sure your PS4 is turned off.
Power off tv.
Unplug PS4 from the mains.
Power off any other hdmi connected devices from your tv then unplug from the mains.
Unplug the tv from the mains.
Remove ALL hdmi cables from the tv. (take a picture, label them etc if you need to end up with them all back in the same inputs)
So now, nothing should be plugged into the mains and nothing should be plugged into the tv.
Walk away, have a cup of tea/coffee/beverage of choice, leave it alone for a little while.
With nothing connected, plug the tv back into the mains, power on.
Power off the tv.
Reconnect the PS4 with hdmi cable in a different input than it was originally connected to.
Plug the PS4 back into the mains.
Power on the tv.
Start the PS4.
You should now have audio through hdmi.
Power off the PS4, then power off the tv.
You may then reconnect the hdmi cable back to the original port if you wish. and check as above.
If all is working, power off again, reconnect any other devices to the tv and plug those back into the mains.
Fingers crossed these steps will help you get things back to normal.
If not, then we'll have to see what else we can come up with.