If you have received the serial number and activation key via e-mail, just copy and paste the serial number and activation key rather than entering it in manually. If entering the serial number and activation key manually, please note that the activation key comprises five groups of four lower case letters separated by space characters.Another possible cause is the activation key that you are entering is not licensed for the version of TTWin3 you are trying to install. For e.g. 3.2.1.0 to 3.2.1.20 can use the same serial number and activation key. A serial number for 3.2.1.x will not work with the next upgrade version of TTwin3, such as version 3.3.0.
Note: Most of the time that we have had queries regarding this issue, it has been caused by human error. An example of this would be incorrectly using upper case letters where lower case letters should have been used. As the serial number and activation key verification process is case sensitive it must be entered exactly as it appears on the License Certificate or email. If the serial number and activation key still refuse to allow installation to commence, please contact Turbosoft support.