This is a limitation of how our gauges communicate between their 2D versions and VC versions. You cannot have the main 2D panel open while also in the VC view. If you require the main 2D view, switch to it using the A and S view cycle keys or by using the the Views menu either at the top of the screen or via the right click context menu to select the "Cockpit" view, which is the main 2D panel. Do not use Shift+# keys to select 2D views in the NGX.
Within the VC, we've provided numerous 2D popups for the DUs, the FMC CDUs, the MCP and so on - these are activated with mouse clickspots and are detailed in the Introduction manual.