Depending on which version you downloaded, you might not be able to access it >.<

You need to have the 'director’s cut' version for all endings to be available, as there is an extra ending in the director’s cut that isn’t in the O2A2 version.

If you’ve got the director’s cut version, did you try following the walkthrough guide here? https://melancholy-marionette.itch.io/the-hostage/devlog/567737/walkthrough-guide

It tells you how to get all the endings :3