Hi,
As Dissonance is a plugin, I would suggest reaching out to the creator for support as they will have a better understand how they have implemented FMOD.
I can however, provide some high level advice.
Are these two buses set up in the FMOD Studio mixer:
In FMOD Studio, we have the FMOD Studio | Effect Reference - Spatializer which could add a directional effect to the audio.
A topic disscussing something similar can be found here: Recommended/usual paths for audio occlusion ("walls block sound") in Unity? - #2 by joseph
Can you please elaborate on this issue?
Unfortunately, as we do not make the Dissonance plugin I cannot comment on the best practice. Hopefully some of this information can point you in the right direction. Please let me know if we can assist further with your FMOD implementation.