I had the very same issue with an FRDM-imx93. Flashing from Linux can be a solution, but if someone else faces the problem, the following worked for me.
When you get the U-Boot shell:
No USB device found USB init failed: -19 u-boot=>
You can try:
=> usb stop
=> usb start
=> fastboot usb 0
If it fails, unplug/replug (board side) only the USB dedicated to serial downloading and repeat those commands. At that point, USB should be discoverable by uuu, so uuu can proceed.
Note that uuu shall continue to run in the meantime (waiting for a USB device to appear).