HiI'm not sure I follow. Are you saying there's an issue with your soundbar decoding from source directly, or are you trying to run it through TV and/or including OTT apps?
There's a soundbar sub-forum if you think the issue is the bar. For the sake of starting with the obvious, I assume you've enabled the relevant CEC handshakes...?
If the problem is the latter one, I don't think there will be enough bandwidth to push lossless Atmos. It should still give you Atmos performance (though lossy), but encoded via a Dolby Digital Plus. You'd need eARC for full Atmos otherwise.
Unless I'm misunderstanding your issue, which is entirely possible.
What I'm doing pushing both sources Fire TV Cube and Nvidia shield Pro 2019 through the HDMI in on bar both Dolby Atmos and Dolby Vision enabled
Tried each source one at a time but cant get Dolby Atmos Signal through both sources the bar only decodes to Dolby Surround sound and not Atmos even if I get lossy Atmos it will be better than Dolby Surround.
But on each source I try Netflix and Prime Video enabled programs I only get Dol y Surround where in theory I should get has yku said lossy Atmos but dont only Dolby Surround.
I have CEc enabled on TV and Sky Q but with Sky Q the Audio id enabled to Dolby Digital plus but that also gives Dolby Surround.
So at a loss why I can't get Dolby Atmos even if lossy would be better than Dolby Surround.
Any help appreciated