Did you buy Pro from
www.limewire.com ? Also, did you purchase less than 6 months ago? When you buy Pro, you have updates & email support for 6 months...after 6 months your email address won't be in the database & so it won't be recognised. If you didn't buy from the official site, likewise your email address won't be recognised
What was the problem - payment issue, trouble using LW etc??