Avaya IPO 9.1.4. We use Plantronics CS540 and another older model of Plantronics headset. When I install a headset on one of our 9608g phones and press the button on the headset to take a call, it does not take the set off hook and allow dial tone in. I can press the headset button and then also press the button on the headset to get it to work, but I would rather be able to just press the one on the headset to get off hook. Am I missing something?