404 error on CS3 Replacement Installer

I purchased a used Mac Mini after unthinkingly updating OSX on my primary computer, which put my copy of InDesign out of commission. After trying to install my old copy of CS3 on the Mini and running into the activation error, I found my way to the Replacement CS3 Installer, but after entering my old serial number there and being given a new one, I get a 404 error message that says the software is unavailable for download. some forums. I tried downloading from a few different locations (in accessing the net) but always got the same response, so I assume the problem isn’t on my end. Thoughts? Is this on Adobe’s end? Is it temporary? Am I doing something wrong?