Before attempting to install or "re-flash" firmware, thorough preparation is mandatory to avoid permanent damage.
Finding specific firmware for a "refurbished" generally means you are looking for the official Stock ROM to restore the device to its original factory state. Refurbished units use the same firmware as retail units, provided the model numbers match. 1. Identify Your Specific Model oppo a78 refurbished firmware
The bootloader is unlocked after a refurbished flash. Fix: Re-lock the bootloader via ADB ( fastboot oem lock ), but note this will wipe the device again. Only do this if the firmware is 100% official. oppo a78 refurbished firmware