The file is incorrectly named or is in the wrong place - please check carefully with the information given in the email. To see if the latter might have happened, open up your license file in any text editor. Each piece of information starts on a new line . The most important information is the license number and email address . These must never be changed.
Some users seem to have emailers which strip out consecutive spaces.
This will result in an invalid license file. A newer version is available from this link . It is not as fully tested as the official release version, but I have found no problems with it. Install it as a User menu item. See the new WinGX installation instructions under section 1.3.3.