If your device shows "Invalid IMEI" or "Baseband Unknown," the NVRAM partition is damaged. Flashing the nvram.bin or nvdata partition from the original MT6731 flash file restores your network functionality.
Ensure the device has at least 50% battery to prevent sudden shutdowns. mt6731 flash file
If your phone is functioning normally, use OTA updates. If it’s bricked, you need the full . If your device shows "Invalid IMEI" or "Baseband