I'm a bit confused - did you ever buy Pro from the official site Lime Wire » Official Website & Free Download, BitTorrent « ?

Membership? - **BEWARE** - Download p2p Clients ONLY Thru Official Sites (click on link)

get your $$$ BACK!!! (music members)

If you didn't buy from the official site (payment to LimeWire LLC) then you're not eligible for Pro support from the official site

There's no registration as such... when you pay LimeWire LLC for Pro, your email address goes into the database so that it's recognised until your Pro benefits run out. But if you've bought Pro from a scam site, your email address won't ever go into the database & so it won't be recognised.