MacBook Pro doesn't recognise external display

Hey Guys

I had my MacBook Pro Mid 2012 13' i5 2.5Ghz 16GB RAM connect to an SAMSUNG screen with a VGA to Minidisplay port , and everything was working fine , until i upgraded to Yosemite!

Since i upgraded to Yosemite , my arragement Tab under Display doesn't appear doesn't mather if the screen is connected or no , it just doesn't appear , and even after plug the screen the screen flashes , but it doesn't recognise it , and still nothing under Display on preferences , i'm using a third party HDMI and VGA to MiniPort Display , i know some you will say its the connector but the true is , some of my friends tried it in their Macs Maverick and Yosemite , and its working fine on their Macs but mine simple disappeared the Arrangement Tab under the Display , i tried all kinda of resets but i can't fix it!

Does some of you know how to help me ?

I would appreciate.

Thank you

Leonardo Miguel