Monitor is disabled?

Hello,

I'm trying to help my mom with a computer problem on her business computer. She has 2 screens working through 1 monitor. The screen on the left is working fine. The screen on the right is saying "no sync" and the screen on the left if also showing that the right screen is disabled. When she tries to click enable it won't allow it. She's checked all the connections as well and all the wires are running fine into the right screen.

Please help if you can.