"Invalid serial number or activation key" Error.
  Please Note: Serial number and Activation keys are used to license TTWin 3.0 through TTWin 3.7. This article does not apply to later versions of TTWin. For information on invalid license type errors for later versions of TTWin please refer to this article.

I am trying to install TTWin3 but I keep getting an error message stating 'Invalid serial number or activation key', what is wrong?

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 example 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. A similar situation occurs for versions greater than 3.8.0 which use certificate files with a .tcf extension rather than serial number and activation keys.

  Most queries we receive regarding this issue are 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.

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