If there's still an entry for the nVidia GPU in the control panel (even if it shows not having a driver loaded), you will need to manually install the Intel and nVidia drivers. If there's no entry at all for the nVidia GPU, it has failed -- if you need it back, you will need to replace the system board.  
Dell Latitude E5440 GT720M does not see the video card It doesn't show up in device manager and bios. I tried to show hidden devices but still couldn't see it  
Dell Latitude E5440 GT720M does not see the video card