How Bootload an Lilypad Arduino USB using Arduino UNO
If you try uploading to a LilyPad USB with the wrong board selected, you may end up in a condition where the bootloader can no longer respond normally. 

You can get the LilyPad Arduino into bootloader mode by tapping the reset button twice in under a second. Once in bootloader mode, the LED should blink at about 1Hz for about 8 seconds. My advice is to load a blank sketch (i.e., nothing in loop() or setup()) and then double tap the reset button shortly after hitting the upload button. That should restore the LilyPad USB to a working state.