Enable on your phone (Settings > About Phone > Tap 'MIUI Version' 7 times > Additional Settings > Developer Options > USB Debugging). Connect your phone to your PC via a USB cable.
If the phone is stuck in Fastboot and not responding to the power button, press and hold (all three buttons) for 15–20 seconds to force a hardware reset. How to Open Fastboot Mode on REDMI A3x
You will see text like FASTBOOT on the screen, along with device info (Product Name, Unlocked status, etc.). Your phone is now in Fastboot Mode. Enable on your phone (Settings > About Phone
Once you are done with your tasks, exiting Fastboot Mode is simple: along with device info (Product Name
Alternatively, use a terminal emulator app and type:
