Second screen not displaying

Hi guys,
A recent issue, my TV has stopped displaying as a second screen.
I am running 1 DVI port to a monitor, which I have infront of me, and have 1 HDMI port to a Amplifier, which then goes to the TV.

The connections appear fine, as running other things through the amp work fine (eg blurays)
My computer still detects the amp, but will not display on it. When i mouseover off my monitor, the mouse disappears but does not appear on the TV.


Display Setup

Edit: I just plugged straight into the TV, and it appears to work, but using it this way would disable use of my sound system.

 

Unfortunately, I didn't end up figuring out (or receiving) a fix.
For anyone with the same issue, I've used a HDMI port on the TV, and set up all sound from the TV to play through the amp also.