my MacBook pro sound is not working. it is off and mute in the sound track and not turning on and stuck too I'm clicking it again and again but the mute bar is ticked and stuck , i just once attached headphones in the mac and suddenly it muted and no sound is coming then i disconnected the headphone but still the same . when i opened the settings checking the sound so no output device for sounds was coming and no input sounds as well. I again and again attached and disconnect the headphones but it was not working and no music was playing on . then i search in internet to unmute the mute bar but nothing helps me although i restart by holding command, option , control , P and R but nothing happens and then shut down the mac again and again as i read the instructions but nothing helped , so finally now I'm sending u this message plzz help me i love my MacBook pro it is the model of 2014 and i loved this mac coz my dad gifted me so plzz help me it is very important for me . the serial number is : C02MPE7MFH00 , Model : A1502 , EMC 2678 Rated 16.5V , Contains : FCC , ID : QDS - BRCM1069 , IC : 4324A - BRCM1069 .