Why can I not see the entire history of my Direct Messages


I’ve been trying to pull up some older conversations I’ve had over DM, but noticed today my DMs from before December of last year are not available through the web app. DMs before April are not available on the Android app. The oldest DM I can retrieve using the REST API (even when setting since_id and max_id) is December of last year.

No DMs are included in my Twitter Archive.

How can I gain access to these (in some cases extremely important) conversations?