I just had some custom Arduinos manufactured, and it's the first time I've included a USB controller, CH340. I'm able to flash the bootloader to the Atmega2560 over ICSP, so the AVR is fine. However when I connect the USB cable, there is no device showing up at all. Its not a driver issue, there is no sound and I doublechecked in usbdeview. Also tried other cables, so I'm suspecting I messed something up in the design since its the first time I'm including USB.
The exact chip used is this one, datasheet. I followed this example when wiring it up, except I have no crystal as the CH340C is supposed to have a built-in crystal.
Anything obvious standing out please?