I've created a game in unity, and now integrating the google mobile ads SDK to set up ads in my game.
However, every time I try to run the game in editor I get the following pop up:

[Just in case the picture is not visiable, it reads "Unable to find jar in the system path. This tool is required to process Play Services dependencies. Either set JAVA_HOME or add jar to the PATH variable to resolve this error."]
I've successfully built and published my Android game, I have JAVA on my machine. So searched for the locations of jar.exe and the added this to the PATH variable in my environment variables settings. However the problem persists - I still get the error message. I even tried creating a new environment variable called JAVA_HOME and puttin gin the location of jar.exe here, but it still doesn't work.
Am I doing something stupid? Does anyone else get this message? Should I just try to ignore it? I haven't tried building the app in unity, but I'm guessing it won't work.
Please help
Thanks
Stephen