I had a Kenwood BT 755 stereo installed by best buy in my 05 Honda S2000 and the tech said He couldn't hook up the mute control on the side dash, is that normal or maybe the tech is wrong, thinking of having them pull it out and reinstalling by someone else? I paid additional $120.00 for those controls to work.

 

That's correct as you need a DCI to work with your new deck.

 

Many (most?) generic aftermarket dash control interfaces don't support the mute button.
For headunits that support a hardwired telephone mute, which I believe your Kenwood does,
there is a workaround discussed in this thread.