Hey guys, while I was trying to unlock the bootloader of my redmi 9 pro max, it showed this error (Unknown error 1004). I search about this error on google to find more details & I tried the given solution from different popular forums like xda, reddit etc but the solution didn’t worked. So I tried doing some random stuff by myself to find the possible reason for that error. After 24 hours of testing, I found the exact reason why there was Unknown error 4004.

This error occurs when we don’t put the original SIM card that we used to sign in to our MI account. This error is also known as device verification failed as the SIM card that we used to verify our account is either not inserted or switch to different one.

The above image shows the error we are talking about. While trying to unlock the bootloader, this is the error message I received.

The solution is simple, we have to insert our SIM card that we used before while verifying our MI account.

After I inserted the SIM cards, the error was fixed & the time remaining to unlock the bootloader just showed up. Here is the screenshot of the solution.

The above image confirms that I was able to fix the error.

Now it is time to unlocked a bootloader on my redmi 9 pro max. Moving forward, I clicked on unlock & followed the steps shown.

The phone got factory erased. Make sure to back up all of your necessary files & apps before unlocking the bootloader.