I have DiscoveryF407VGt6 board, I did try both of "STM32F4-Discovery_FW_V1.1.0" and "en.stm32cubef4" demonstration examples. LEDs work fine by both examples, but there is no mouse action at all!
Which USB connection are you using?
Mini USB for power supply and Micro USB for using board as mouse, both at the same time!
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