[movie78]

Are the files you're playing definitely Atmos?  Debug log?

Here is the log file.

Debug log 

From what I can see in your log it says no pass through, so you either don’t have it set correctly or the edid on your sound bar reports incorrectly, this could also be a signal/ handshaking problem.
What are your shield output settings regarding audio, what are your audio settings in Kodi? 

Every other app on the shield plays bitstream without any issue and Kodi passthrough is enable.