This link's to the official site, you'll see that it shows the price of Pro for 6 months & 12 months.
Lime Wire » Download LimeWire

4 - 5 months ago, Pro cost $24.95 for 6 months & I'm pretty sure that it was still $34.95 for a year's worth.

So...it sounds like you didn't buy Pro from the official site. In that case, your email address wouldn't be in the official database & that's why it won't be recognised. Only people who've bought from the official site can download Pro installers from that site.