If you see a yellow exclamation mark or it shows as "Unknown Device": Download the official Qualcomm USB Drivers.
A low battery can prevent the device from staying in EDL mode or cause it to disconnect during flashing. Most guides recommend the battery be at least charged. Also, try different USB cables. Many cables are charge-only. Ensure you use a good quality data cable . qfil failed to open com port handle
For deeply bricked devices, you may need a specialized EDL deep-flash cable, or you must short the physical test points on the device's motherboard to force the QDLoader 9008 state. Best Practices for Using QFIL If you see a yellow exclamation mark or
QFIL will now see a virgin port with no cached state. Also, try different USB cables
A bad cable, loose port, or USB 3.0 incompatibility is disrupting the data stream.