Warning: Selecting "clean all and lock" will relock your bootloader. Only do this if you are sure you are flashing the correct regional firmware.
Turn off your Redmi 6A. Press and hold Volume Down + Power simultaneously until the Mi Bunny logo appears. download firmware redmi 6a cactus global fastboot rom
Install these so your computer recognizes the phone in Fastboot mode. Warning: Selecting "clean all and lock" will relock
Follow this comprehensive guide to find the right files and install them safely. Official Redmi 6A (Cactus) Global Fastboot ROM Details Press and hold Volume Down + Power simultaneously
Xiaomi devices require an officially unlocked bootloader to flash via Fastboot.
Flashing a Fastboot ROM wipes all internal storage. Backup your photos and contacts first. How to Install Redmi 6A Global Fastboot ROM
Download the latest version of the Xiaomi Mi Flash Tool on your PC.