Cannot get passthrough to work with my AVR

I have been running the same setup for years, Windows PC running Kodi (always latest version) Dolby Digital (non-HD) receiver using HDMI.

I temporarily moved to a place where surround sound was not an option so I was running all my sound directly to my TV via HDMi. Now I am back and want to start using my 5.1 setup like I always had but no way that I set my audio settings within Kodi allow Dolby Passthrough. All I get is PCM on my receiver.

Below are my settings I have always used. I have also tried WASAPI HDMI rather than DIRECTSOUND with no change. I know my receiver is working because I can play Dolby Digital when viewing Netflix.

Any help would be greatly appreciated.