Websites promising free registration keys frequently bundle downloads with spyware, ransomware, or trojans.
If you are unable to find the serial number, or if the number is unreadable: dfx serial number
Double-check the characters entered into the registration box. Software keys often confuse the number "0" with the letter "O," or the number "1" with the capital letter "I." Copying and pasting the code directly from your confirmation email eliminates manual entry mistakes. Server Connection Failures dfx serial number