You'll need the F4 board to be plugged in via both usb cables for it to work properly - that may be your issue.
Otherwise I really can't offer much support for non-espruino boards I'm afraid.
@Gordon started
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
You'll need the F4 board to be plugged in via both usb cables for it to work properly - that may be your issue.
Otherwise I really can't offer much support for non-espruino boards I'm afraid.