When you say it's not working, did it download, but not install, or are you not getting a download ?
If it downloaded but won't install, the serial number is case sensitive and must be entered exactly as shown. Suggest copy and paste. It is better than manual entry. If you must manual entry, remember there are no alphabetical I's or O's. They are all numerical 1's or 0's.
If it seems to have downloaded and you are getting a message telling you the links have been used up when you try to download again , then that could be because there is a download accellerator installed in your system which zapped the download, and ate up the remaining links. If that's the case, send an email to
dougc@mtu.com and explain the situation.
George