Trying To Reinstall Adobe Acrobat 9 Standard - Our Serial Number Is Coming Up As An Upgrade?

Good morning,

So I was tasked to replace a workstation for one of the users here at my workplace, and migrate his software.

Retrieved Adobe Acrobat 9 Standard installation disc we had, and our last known serial number for it.

During the re-installation, it accepts our serial number and goes through the process.

When it completes, all of a sudden the window comes up saying that they key we used was actually an upgrade key and is asking us for the serial number of the previously used version.

Problem is, there was no previous version. The older workstation and its Adobe Acrobat 9 Standard installation was working fine, no problems with the key before.

Now, if I had forgotten to deactivate the previous workstation, I would have gotten a different error, right?