I have a Naga v2 HyperSpeed.
I haven't been able to use special buttons for a few months or versions.
When Synapse is closed, only some buttons that don't require Synapse work such as "Volume Up", others don't work, such as "Show Desktop".
The interesting thing is that when Synapse is open, none of the special buttons work, only right-left click and scroll work.
I tried clear reinstal Synapse 3 and 4, created different profiles, the result didn't change.