Handy tool to reset the usbport remotely after you flashed a new firmware update which upsets the USB stack on the raspi.
compile with:
gcc usbreset.c -o usbreset
Assuming you have your YF plugged into one of the USB 2.0 ports (black connector) on a raspi 4 run:
sudo ./usbreset /dev/bus/usb/001/002
then restart rosserial. This should help with rediscovering the CDC serial port after you have flashed new firmware onto the mainboard. The alternative is to unplug/replug the USB cable.