January 17, 2019

We’ve become aware of an issue in Twitter for Android that disabled the “Protect your Tweets” setting if certain account changes were made. You may have been impacted by this issue if you had protected Tweets turned on in your settings, used Twitter for Android, and made certain changes to account settings such as changing the email address associated with your account between November 3, 2014, and January 14, 2019. People on iOS or the web were not impacted. We fixed the issue on January 14, and we’ll provide updates if other important information becomes available.

https://help.twitter.com/en/protected-tweets-android