Users typically see this error in the following situations:
These methods may require entering BROM mode (holding both volume buttons while connecting to a PC). 4. Physical Check If the error appears spontaneously: Check if your Volume Down key is stuck or shorted.
This error typically occurs when trying to unlock the bootloader using fastboot oem unlock or fastboot flashing unlock .
If there is no official Deep Testing APK for your specific model and regional firmware version, Using third-party "unlocker" software often results in a hard-bricked device because the vbmeta and signature checks remain active. Summary Checklist Is Deep Testing approved (Review Successful)? Are you using the original USB cable? Does the phone show "Fastboot Unlock" mode specifically? Have you tried both oem unlock and flashing unlock ?