CameraReservedByAnotherApp seems to be an error generated by Windows 10. It would suggest that another program is claiming access to the camera first when you are trying to use it.
As you got that mesage, the first thing I recommend trying is to find out if you have the RealSense Virtual Driver successfully installed. The Virtual Driver was originally created with the intention of enabling a non-RealSense program to access the camera if a RealSense app was already using it.
If you open your Device Manager window in Windows and look for the RealSense drivers (they are usually either under the Imaging Devices section or a Camera section), there should be three drivers listed for the SR300: RGB, Depth and Virtual Driver.
If the installation process has left out any of these drivers, it can cause the camera to not function properly. Without a full set of drivers present, the camera is treated like an ordinary video webcam rather than a RealSense camera.