How to login to resetted phone when verified password not accepted?

Question

I reseted my Oneplus 2 phone with OO3.5 by wipe cache and data because I wanted to set up my business gmail in my phone, not my personal:

Wipe data and cache

Volume down + power > Format phone

Now, welcome screen where it does not accept my personal email account's password now
- Status in OO support: unable to access or add on your Google account

Both of the gmail accounts uses my personal phone number as the primary, and in some field my personal email address.

Now, the phone requires after volume down + power for 15-20 seconds - - to use the gmail account (personal gmail) which I used before in the phone (some protection mechanism).
However, it does not accept the password which I enter to my account, although I put the correct password (verified at Desktop).
I am trying to pass FRP (Factory Reset Protection) which requires you to login with a previously synced account on that device and you won't use the device.
I have a Desktop access to my Gmail where I can access it.

I have throubleshooted settings here but cannot find anything relevant there.
I also erased all data in the phone by those settings.
However, I am not sure if it is applied because I wiped the data and cache before that.
I know the threads but they do not help

How can I unlock my phone? I locked it using Android Device Manager, but it claims I entered a wrong password

Android lock screen won't accept password from Android Device Manager

Things which I have tried to do with login unsuccessfully

use 2-step password

use app password for the task

use my own password for the task

Error when entered correct password in Android (password verified in Desktop)

The password is incorrect. Try again.

Troubleshooting in `fastboot` (volume-up + power) by following the guide here

The command adb devices gave first time the device ID.
So I could do fastboot oem unlock and fastboot reboot.

Result: still does not accept my personal gmail account password.

Trying to get to recovery

Now in fastboot, adb devices gives blank. I cannot get to adb device recovery.

Troubleshooting proposals tested but failed

Keyboard-button-bug (here) fails because the bug has been removed in the keyboard layout.

Other strategies presented in the thread One plus two Google lock frp do no work.

Troubleshooting with OO support

May we know what happen prior to this issue, was your phone recently flashed? And also, what is your current OS version?

No. I upgraded it to OO 3.5 some time ago.
Prior to this issue, I just reseted the phone because I wanted to change my Gmail account and do reseting.

Phone: Oneplus 2

Android: OO3.5, Android 6

XDA thread post about the issue: here #11

— LÃ©o LÃ©opold Hertz ì¤€ì˜ | Sources

Answer

Oneplus support says

Since your account was not recognize you need to wait at least 72 hours to recognize you credential. - - This is between google and OnePlus protocol. - - Make sure not to enter again otherwise it will reset again the waiting time.

So because Oneplus is not Google's, you have worser support. You have to wait 72 h last time you inserted the password as "incorrect".

Option 2

Either a remote session would fix but we only have 28th of this month schedule or wait for 72 hours. - - The remote session is flashing the device but we will wipe all the data. - - But I don't have available schedule until next Saturday .

So they are in under-capacity, and cannot fix the thing faster because of the protocol difference between Oneplus and Google.

Factors

2-step verification on

History of attempts

Sunday, 22nd jan 3 pm, I ordered Google delete data and everything from my phone, but the mechanism never apparently ended because Google's site javascript about the thing just stayed as [trying to complete]

Sunday, 22nd jan 4 pm failed login with the real password

Wednesday, 25th jan 7 pm failed login with the real password

Saturday, 28th jan 2230 failed login with the app generated password

Activate Option 2 with Oneplus support by providing them both IMEI numbers (1 and 2) 29th Jan.

Tuesday, 31th 2330 pm attempt failed with the real password

4.2.2017 attempt fails because no file transfer possible to Oneplus phone

OO Support plan for recovery

I received the piece of advice to flash back to 3.1.0 but no certainty that it will help

Flashing guide for OnePlus 2: Downgrading from 3.5.5 to 3.1.0 - - Steps: 1) Download 3.1.1 Intermittent Version and 3.1.0

I could not complete this stage because I could not transfer the two ROM files to the memory of the phone. There is no memory card slot in the phone.

15.2.2017 session with Tech 2 level

They allow only Windows based system for the recovery with the techincal support of 2 level.
They run some Chinese frontend there so very difficult for me to say what is going on.
They initially shared some links about the data files which download processes were difficult because of interrupted connections with one file.
The session time ended after some initial corrections in the system (not specified).
The result is that the phone starts but does not detect Sim-card and restarts automatically after each 5 minute.
I ordered the second technical session.

Had to be persistent for scheduling 2nd technical support

To schedule a new remote session appointment, kindly contact our live support channel to assist you a new remote session schedule.

Okay thank you. I suggest you to contact the Amazon UK. All devices bought from Amazon UK will go through to their assistance.

This way, OnePlus was going to reject the case. - - Now, they changed their mind (after pressure here), and accepted me to another tech session because they scheduled too little time.

Details passed to the engineer after the first tech 2 support, for the second tech session on 22nd Feb at 1800 PM my timezone

current state: phone starts, but does not detect sim card and restarts itself all the time.

This troubeshoot session also failed in the same condition.
We did second time the restore session with 2nd level tech support of OnePlus.

Final decision

I claimed the warrant and shipped the phone back to Amazon.co.uk.
I will get full refund.