Adobe officially ended support and technical assistance for Acrobat 2015 on July 7, 2020
Adobe Acrobat Pro DC 2015 won't let me log in after reinstall
The software term "Adobe Acrobat Pro DC v2015 Multi-XForce 2021" typically refers to an unauthorized, pirated version of Adobe Acrobat. Specifically, "X-Force" is a well-known name for a group that creates "keygens" or "cracks" used to bypass software licensing and activation systems .