When you say it starts on your monitor, do you mean a rift output or a normal output? I assume a normal output, in which case have you gone into your settings and tried selecting Oculus as the 3D 'with headphones'? It may have reverted back to default graphics settings.
Also, are you using extended mode? Would recommend using that, seems to work best. Because if you're getting a rift output it suggests you have it on direct. Make sure your camera light is on as well to indicate it is picking up the rift correctly. Could try restarting services as well, although I had a few weird issues that would only resolve after rebooting the machine.