Follow the instruction in locating SDK Platform-Tools for Windows
Windows
Depending on which version of Windows you’re using, these steps may be slightly different. To add ADB to your PATH variable, follow these steps:
Open the Start menu and search for “advanced system settings.”
Click “View advanced system settings.”
Click the box that says “Environment Variables.”
Under “System variables” click on the variable named “Path”.
Click “Edit…”
(Windows 7,8): Add ;[FOLDERNAME] to the end of the “Variable value” box, replacing [FOLDERNAME] with the folder path where you extracted Platform Tools. Be sure to include the semicolon at the beginning so Windows knows you’re adding a new folder.
I am also facing this problem and it is not a proper solution of it. I want help to solve it. and live testing through companion is always crashed after some seconds.
I encounter the same problem and i have got temporary solution which is when the error message appear press Esc button until it disappear, Actually it disappeared in 17 times Esc button press but when you press you should wait when the error come unless it will exit from companion, when it disappeared you have to wait until assets loaded