Creo 3.0 Accademic License error

Hello PTC Community,

My name is Andrea, I have already installed Creo 2.0, but now that I have Windows7 I could afford the newer 3.0 version. I couldn't find a link to download the file again so I had to register once more. Followed the instructions and everything seemed to work except for when I got to insert the code received in the pdf. After the elaboration it just says "Error" in red without any specific information, so it couldn't recognize my License. What am I doing wrong?

Thank you all in advance

Andrea