The gnutella.net file's inside LW's preferences folder...so if you found the gnutella.net file then you also found the prefs folder but maybe didn't realise it

Is this the link that you were using to enter your email address(es)?
Lime Wire » LimeWire PRO Support Center

Do you still have the email that LW sent you, after you bought Pro? That will have a link to your personal download page (where you go to download your Pro installers).

Who did you pay for Pro?
If you bought from the official site Lime Wire » Official Website & Free Download, BitTorrent « are your Pro benefits still current? If you bought 6 months worth of Pro, it needs to be less than 6 months since you paid. Did you buy Pro or Extended Pro?

If you did buy from the official site (payment to LimeWire LLC on your CC statement) but your Pro benefits have expired...you won't be able to download a new Pro installer for free.
If you didn't buy from the official site then your email address would never have been in the official database & you won't be able to download a new Pro installer for free.

Within the help thread If LW Will Not Connect is a link explaining the details that we need.