One computer crashed with the license, so I downloaded it on a temp computer. Now I have a new computer that I am trying to license my software on. It says the serial number is invalid. I signed out of Lightroom on the temp computer and uninstalled it. I am not a creative cloud subscriber. My license is registered in my Adobe account.
I can't find a contact phone, email nor chat window to help me.
I assume you've got Lightroom 6. Which operating system?
Can you post a screenshot of the exact error message?