Available Installs

I just downgraded from Windows 10 back to Windows 7 because the new OS kept crashing.

I'm trying to reinstall Norton Internet Security and it's telling me I don't have any installs left. I currently have only one computer running NIS (after deleting licenses from the other 2 to free up licenses as instructed) and as I understand it I should have 3 installs total.

How can I reinstall NIS on my computer with my newly downgraded Windows 7 OS, and how can I get all 3 licenses for the product instead of just the one?

<frustrated>