Unable to share content on HDX 4000

I am using HDX 4000 model.Some times before, i had to factory reset my unit. since then, I am not able share content through PC. When I press content button on keypad, it is showing content  for few seconds and then error message comes saying 'No VGA signals can be detected'

I have also checked VGA port connection and tried replacing VGA cable but nothing seems to work.

Can anybody please suggest about possible workaround?Should i change the PC from which i am sharing the content or is there any issue with my VC unit's VGA port.

Thanks in advance