The screen will go black. The PC should detect it as "Qualcomm HS-USB QDLoader 9008". :
If software commands fail, you must open the back cover and short the "Test Points" on the motherboard while connecting to USB. vivo-fastboot-bootloader-unlock-reboot-fb-to-edl
: Install Vivo USB Drivers and ADB/Fastboot Binaries . Battery : Ensure the device has at least 50% charge. Phase 1: Boot into Fastboot Mode The screen will go black
For newer models, use the (APK/PC tool) to request the unlock permissions first. vivo-fastboot-bootloader-unlock-reboot-fb-to-edl
Where to find the for your specific chipset? How to verify the COM Port in Windows Device Manager?