DTM is Desktop Manager and search BlackBerry Technical Solution Center
for clean uninstall and you will find the article.
What happens when the user tries the activation? Is the user receiving the email with the ETP.dat attachment? If not the he or the Exchange server is filtering it. If he is getting it then he may have a mailbox issue, that might explain the unable to get more issue. But there are other things that can be checked first. You can also search the above link for enterprise activation, there is a great article for troubleshooting enterprise activation.