ATMega32u4 says its only USB2. So the problem is the PC driver it not backwards compliant? Or the PC hardware is not backwards compliant?
USB 2.0 Full-speed/Low Speed Device Module with Interrupt on Transfer Completion
– Complies fully with Universal Serial Bus Specification Rev 2.0
– Supports data transfer rates up to 12 Mbit/s and 1.5 Mbit/s
– Endpoint 0 for Control Transfers: up to 64-bytes
– 6 Programmable Endpoints with IN or Out Directions and with Bulk, Interrupt or Isochronous Transfers
– Configurable Endpoints size up to 256 bytes in double bank mode
– Fully independent 832 bytes USB DPRAM for endpoint memory allocation
– Suspend/Resume Interrupts
– CPU Reset possible on USB Bus Reset detection
– 48 MHz from PLL for Full-speed Bus Operation
– USB Bus Connection/Disconnection on Microcontroller Request
– Crystal-less operation for Low Speed mode