Offline activation - Framemaker 12

I bought a perpetual license for Framemaker 12 back in 2014. I need to use it on a new computer. I signed out/deactivated it on my old computer but can't get the serial number to take. I contacted Adobe support, who confirmed that I do have a valid license and gave me instructions for offline acctivation. My problem is that step 2 says "click Having Trouble Connecting To The Internet" but I have seen no such link or similar.

So I'm stuck at a screen that says my serial number is already in use by the maximum allowed computers, which can't be true because I already logged out of Framemaker on my old machine.

Any ideas how to fix this?