Problem connecting MacBook to TV
When you say screensaver, do you mean a static image or a mountain or something like that?

It could be that previously your computer was previously mirroring the image from your MacBook's built-in screen to the TV, and it has for some unknown reason switched modes and is now creating a second desktop.

Computers like yours can support up to three screens including the built-in one, and you can mix and match the mirroring and desktop modes.

Spanning basically gives you more room, it allows you to put windows onto the second screen and you can move your mouse between them, but in this case it's not what you want.

You can verify if this is what is happening by following these steps:


Click on the Apple menu
Open "System Preferences"





Choose "Displays".





Select the "Arrangement" option.


If this option is missing then the problem is not what I suspect, please come back and let me know.




You should see a diagram that shows you two blue boxes side-by-side:




This diagram shows how the two screens are arranged in relation to your mouse and the laptop, the one with the white bar is the primary screen (probably the build-in screen).

If as with this diagram the second box (without white bar) is off to the left you should find that if you move your cursor to the left if will appear on the TV.

If this is the case the solution is simple, there are two ways:

a. Press CommandF1 to switch into mirroring mode.

b. In the System Preferences window you have opened click "Mirror Displays" 



After you've done this you'll notice that the blue boxes are now stacked in the System Preferences window, this indicates they are displaying the same image. The system should remember this in future, it is possible this was reset by the system during a firmware update caused by a software update you ran on your computer.