Problem to update firmware using bootloader to PIC18F4550
See the below section of the data sheet- there may be other things wrong (the clock has to be correct) but it certainly won’t work without the cap on Vusb.


  17.2.2.8 Internal Regulator
  The PIC18FX455/X550 devices have a built-in 3.3V regulator to provide power to the internal transceiver and provide a source for the internal/external pull-ups. An external 220 nF (±20%) capacitor is required for stability.