Model Viewports is grayed out

I'm new to AutoCAD 2015 from 2011. I'm trying to create a new single viewport on a new layout tab. On the View Tab I find the Model Viewports but it is grayed out and won't allow me to add a new viewport. I can type in "Viewports" into the command line and add a viewport using the dialog box but would like to use the icon method rather than having to take the extra steps. Any suggestions on how to change the Model Viewport so it's not grayed out?