Are you trying to or just flashing firmware ? What is the exact model of your phone?

Use the original USB cable; many third-party cables only support charging and not data/DIAG protocols.

The most common use case is . If a device has lost its IMEI numbers (often due to a firmware corruption or a failed flash), they cannot be written back through normal means. A diag port connection is typically required to re-write these numbers.

If the phone just turns on normally when you plug it in, your timing is off. Try holding the buttons before plugging in the cable, or try a different button combination (Power + Volume Down).

Before executing any commands or handling hardware buttons, your Windows system must be properly configured to identify the temporary serial connection. 1. Install Authoritative Spreadtrum/Unisoc Drivers

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