What is the "unrecoverable" state?
A state where the Android device owner realizes that he/her cannot recover
- There were no devices having status of "logging in" ( All devices had already logged out )
- The device-owner ran out of back-up codes ( There were no codes thatmade the device-owner log in ）
- When the device-owner entered "E-mail address" and "password" in the login-window at google.com, the error-message "Could Not Verify Your Account" was displayed with the hyperlink of "Account Recovery"
- When the device-owner entered "E-mail address" and "password" in the "Account Recovery"-window at google.com, the error-message "Could Not Verify Your Account" was displayed
- When the device-owner entered the "Recovery Email Address" in "Account Recovery"-window, a confirmation-code was sent, but the device-owner cannot log in using it. The device-owner got the error "Could Not Verify Your Account".
- The device-owner asked Google Official Twitter Account to recovery his/her Google Account at Twitter. Google's operator began teaching the device-owner to recover it. However, the device-owner failed in recovering his/her account.
The trigger of recovering
One day, all contents in micro SD was deleted. There was no evidence of intrusion from the outside.
It was only possible that ROM that the device-owner downloaded from the device-maker-site when he/she had rooted the device was contaminated.
The device-owner remembered that his/her device had a lot of bugs. For example, he/she hadn't recovered in-app purchase in some apps, an uninstalled-app-tab in the app-history of "Google Play Store"-app was loading forever.
So, the device-owner investegated "Google Play Store"-app, and he/she found there are no links of "Update the Play Store" and "details" in the "Google Play Store"-app.
How to Recover
The device-owner re-rooted the device with the same ROM downloaded from the maker's site and replace installed "Google Play Store"-app to one downloaded from apkmirror.com. Then, links of "Update the Play Store" and "details" appeared, and the in-app purchase in some apps and an uninstalled-app-tab in the app-history of "Google Play Store"-app were immidiately loaded.
As a precaution, the device-ownder replaced "Google System WebView"-app and "com.google.android.gms".
Done with it
In consequence of replacing to apps dowloaded from apkmirror.com, the device-owner could add his/her "Google Account" that was maarked as "Unrecoverable" at "Settings" > "Account" > "Add Accounts". The device-owner didn't need to do "Acount Recovery" at google.com.
When the device-owner logged in to the restored account at google.com and looked at the "Device Management" tab, only one name of the device currently using was displayed in the "Logged in device" column. The device wasn't hijacked.
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