Hmm.Thats weird.

I had this issue with other phones and happened because of a bad persist corrupt.
Enter fastboot by: keep holding power + vol down and connect to pc.If you feel any vibration that means its on.If device is not recognized then leave the phone overnight in charging and try again.If you are in fastboot.Write 1.fastboot oem unlock 2.fastboot flashing unlock_critical.
3.fastboot reboot edl and flash the latest fastboot rom for mi a2 using mi flash.