No sound output from external monitor after closing the lid on macbook pro

[howareyoukk]

So I am connecting my macbook pro to an external monitor via mini display port to display port cable, and the cable does carry sound. The cable works fine and I can hear sound most of the time from the external speaker if i dont close the lid on my macbook as the laptop is still connecting to the monitor. The moment I close the lid, i will no longer receive any sounds from the external speaker. I will only receive the sound from the internal speaker instead. I went to system preference-> sound and it shows me the external sound output is the monitor itself but i am just not getting any sound from the external speaker. I can solve the issue by restarting mac but i am just wondering if some of you encounter this kind of issue as well and possibly find a way to fix it

Thanks in advanced