Activating Acrobat

I have an older version of Adobe acrobat Pro (8.0, I think) that is fully licensed and I have the license number and entered it and it was accepted. Unfortunately when I start up Acrobat on my Mac where I entered the license number, it consistently tells me that I don't have an Internet connection and it's unable to activate Acrobat. I have been using acrobat pro on this computer for years, prior to creative cloud, and it should still work. It's licensed, paid for and has been used again for years. Any idea why it's telling me this? My internet connection is working fine. If I hit "try again" it just closes. Thanks. (see screenshot)