black csreen hen tying to cast mb to my samung tv

Do does anyone  have any idea what I'm doing wrong. When I link up my MacBook pro with the TV,  all I get is this black screen with a row of dots at the top and my MacBook pro mentioned on the center.   I think it might be sharing sound but there's no picture
There are controls on the screen to play, fast Forward and reverse but they don't do anything. I can turn the screen off and exit the black screen but nothing else I have turned on screen sharing reset the Bluetooth turned on screen mirroring, nothing helps. Do you have any idea what I'm doing wrong?  Could something in my MacBook pro be preventing it from sending a picture to this external screen?