I loosened the bracket screws on the base and this resolved  the issue. I found that the metal clamp pulls the contacts apart between the clamp unit and the main unit. For some reason when you tighten the screws down with the metal clamp it puts pressure on the clamp unit and doesn't allow a good connection. If the unit feels that it has any movement or not being held securely, I recommend to use the 3m thin adhesive double stick tape provided with the additional clamp set provided in the kit, this should create a firm grip and hopefully resolve any movement.  Since most of our helmets have a curve when we are attempting to attach the units they create a deflection in the contact points of the mounting base.  I backed off the screws while listening to some music and placed the helmet on my desk while backing out the torque screws and was able to hear it kick on. Give this a try it worked for me and now a happy Sena user with both speakers working.