If you use the new built-in Win10 Skype and get the "your Webcam is using another program" message and will not display video in the Test switch...then all it needs is this: -
Enter Start>Apps & Features>Skype and click. Select Advanced Options then Scroll down Select RESET and done. No need for a reboot. Just restart Skype. It will then ask if you want to allow Skype access to the Cam & Mic. Others have managed to resolve this simply by switching ON Permissions in Settings in Start Menu which this also does now.
It keeps on happening this. I found out the better way rather than RESET is use TERMINATE and restart it. Somehow closing the program or others is not stopping access to your webcam & mic!