check if you are using usb 1.0 or 1.1 ports. I had problems with usb 2.0 for cold flashing (and my usb 3.0 ports not working with flasher-3.5)

next make sure you are using 32 bit version of some linux distribution (some 64 bit has problem with 32 bit version of userspace)

and also provide output of your flasher commands. before cold flashing phone must be (fully) charged and turned off.