On an option 61c our receptionist phone quit answering when people dial 0 from our main number menu. It quit answering right after I installed a plantronics headset. Now it won't work with or without the headset. When you hit zero at the menu it says "Were sorry your call can't be completed at this time, try again later." I checked the menu options and the revert DN is set to the receptionist number. I've tried disconnecting and reconnecting the phone. When I prt the DN of the phone it says LDN. I am supposed to have this working by morning.