Atmos downmix to 7.1 mix export > wrong playback wrong channel order

I’ve been setting up my 5.1.4 speakers and doing room correction (basic level adjustments and signal delay with MixerDelay) all seems to have changed things for the better.

Now I’ve finally started some test mixing and run into issues with exporting the file for playback outside Nuendo.
I’ve tried a interleaved file and multi-mono/split, but I can’t get a file that plays well on my Mac Studio (Fireface UC) or on my MacBook via HDMI to my 7.1.2 sound-bar.

I’m not sure what is wrong but in Acoustica Premium I can import the multi-mono files but it stops at 5.1. So I think the extensions is incorrect.
Here are the filenames (alphabetical order).

MA-TD-DA-v3-71.C.wav
MA-TD-DA-v3-71.L.wav
MA-TD-DA-v3-71.Lfe.wav
MA-TD-DA-v3-71.Ls.wav
MA-TD-DA-v3-71.Lss.wav
MA-TD-DA-v3-71.R.wav
MA-TD-DA-v3-71.Rs.wav
MA-TD-DA-v3-71.Rss.wav

Also tried RX and AudioEase Snapper but that does not work.
When I playback the 7.1 interleaved on my sound-bar the C is on the Ls speaker…

Is this a known issue or am I doing something wrong…

Thanks for tips!