Can't register on a new computer?

I bought a digital copy of FFX|V a few weeks ago, loaded it on my old computer and played for a bit (level 10!). I was busy the next few days after that then got a new computer. I assumed I could just load up the client on my new machine and get back to playing on my old character. When I downloaded the setup file and ran it it asks for my registration info. I entered it and got an error about how this code was already used.

My question is: can I not use the copy I bought anymore? The old computer is gone or I would just use that for now. Do I really need to buy a new copy to play on a different machine? I opened an email ticket with SE but they have not responded other than to say they would get to me in 2 business days (4 business days ago...).

You just should have chosen the option to use your existing SE account nothing more.
You can play from various computers as I do it too.

There was two options I currently possess a Square Enix account and I do not currently possess a Square Enix account. I picked that I did possess a Square Enix account and then enter my account credentials and it goes to the registration code entry screen. Is there maybe an old version of the setup utility that I am using? I wonder if I can find another one.

I'm having this exact same problem. I started a thread for my issue also. I can't access it on either my old laptop or the new PC. I'll let you know if I get an answer that works.

as long as you registered your code to your SE id, you shouldn't have a problem..possibly issue on SE's side

Okay, I did some more digging and I think I found out the problem. I was using an early access code that I guess stopped working. To fix the problem i went to www.findmyorder.com and entered my digital order information from my confirmation email. The website then game me the 20 digit code that is linked to my digital order. The updater is currently downloading the game, so I think it worked.