I had the same problem, and when I took a look at the plugin files, I noticed that the auto-install had put the “runPHP” folder inside another folder called “runphp.” I compared it to another install that had previously had the plugin installed/running, and realized it should be (your plugin folder)/runPHP/(files), not (your plugin folder)/runphp/runPHP/(files).
I moved the folder to the appropriate place, activated, and it seems to be working fine. 🙂
