If you are helping a client upgrade to a newer tablet and signing into a personal Google account on the new tablet, you might encounter a security prompt that prevents you from being able to sign into the account, even with the right password.
The easiest way to avoid this issue is to first remove the Google account from the original tablet before signing into the Google account on the new tablet. These steps should be followed on the tablet that you will be retiring.
Once this process is completed, you should be able to log into the Google account on the new device without a security prompt being sent to the original tablet.