So here are the details:
Firstly cannot add account in Mi Unlock Status -> Add account and device. It always gives an error couldn't add error code 86012. and ignoring this if I try to proceed to unlock than I get current account cannot unlock this device. These days im getting couldn't verify, waut or minute or two. But nonetheless error is still the same.
I have tried using another sim card but got the same error on that account also. I contacted customer services but they couldn't do anything.
I have tried each and every suggestion I have found so far. keeping find device on, logging on to i.mi.com, usb debugging enabled, using VPN services on the device to add the account, running unlock tool as administrator, using multiple accounts both on device and PC, Driver signing off, etc, etc....
One thing which surprised me was I tried to unlock without having signed on to any account on my device. I had signed out of my MI account on my phone and then went to fastboot and tried to unlock and guess what? It still gave me the same error!!!!
I had expected to get a different error suggesting that I sign in on the device but that didn't happen.
Also I tried with different accounts on the device and the tool. signed in with account A on phone and used account B in unlock tool and still I got the same error!!
I hope someone might help me.