Sound – no compressed formats found

Hi all, hope someone can help on this.
Used kodi for ages, but this is the first time I’ve tried with an intel NUC 3217BY (HD graphics 4000).
Set up is nuc attached to hdmi matrix…matrix to TV or projector…matrix also provides optical out to an AC3 decoder.
I can’t get passthrough to work and it seems to be a windows issue as in the properties it says no compressed formats found, not even AC3/DTS. I’ve made sure that the intel management engine is installed and all drivers up to date.
I’ve tried 3 different TVs and a benq projector in the setup. All results the same. I know the setup should work because if I use a raspberry PI3 with libreelec, audio passthrough is fine.
Unless I’m mistaken I need to use audio passthrough because the matrix is connecting to decoder by Spdif. So 2.0 channels and passthrough selected in audio options.
Any ideas how to problem solve?