Did you buy Pro from the official site? Lime Wire » Download LimeWire
Did you pay LimeWireLLC for Pro (check your CC statement)?

If you paid a scam site for Pro then you won't ever be able to update from the official site.

Did you buy Pro for a year or 6 months? Your email address will only be recognised in the official database while your Pro's current - if you bought Pro for 6 months, your email address stays in the database for 6 months, if you bought Pro for a year then your email address stays in the database for a year.

After you bought Pro, you would have got an email from LW with a link to your Pro personal download page. Have a look through your emails & see if you can find it.

If you're sure that you bought from the official site & your Pro's still current, send an email to limenathan (click on link) & explain what's happened