How To Solve Locked Account Issue Associated To Gmail

Google is the big giant that believes in keeping its products and services according to the policies. In case, if Google will found any unusual and threat related activity on your account then it will restrict you from using the particular service. For protecting your account from fraud or abuse, it may happen that Google will temporarily suspended your account. As per the Google, following activities may lock down user account that may lasts from a minute to twenty four hours depending on the behavior of the account usage detected by the system. 

Source: http://snakepoke.over-blog.com/2017/08/what-are-the-incidents-when-your-account-get-locked.html