I have a strange issue that I can not seem to find any record of but it has now happened to me on two separate machines! I am building Windows Phone 8.1 apps and testing them on a physical device. This works fine for a time until at some point with no warning i am unable to deploy to the phone and the console shows the errors below!
Error : DEP6100 : The following unexpected error occurred during bootstrapping stage 'Connecting to the device '30F105C9-681E-420b-A277-7C086EAD8A4E'.': SmartDeviceException - Deployment failed because no Windows Phone was detected. Make sure a phone is connected and powered on.
Error : DEP6200 : Bootstrapping 'Device' failed. Device cannot be found. Deployment failed because no Windows Phone was detected. Make sure a phone is connected and powered on.
Now this would lead me to believe that the cable has fallen out or its just become disconnected however it hasn't and im sure of that because i can still use it as a storage device to transfer pictures. Restarting the devices has zero effect and the only thing that worked on the first machine i tried was reformatting the pc and starting from scratch which i really dont have the time to do again!