Redirecting the Attachments Page to the Attachment File

Hello,

I’m trying to redirect links to attachment pages to the attachment file retroactively (to work with Lightbox 2). I know how to implement it going forward, but can someone help doing it retroactively?

I’ve followed this tutorial, but it is not working:
https://www.wpcloudlayer.com/redirecting-the-attachments-page-to-the-attachment-file/

on links in question, it returns false instead of true, so it is running, but it’s not id’ing/changing attachment links.

I am testing on a child template of the twentyten theme.

Thanks!