Hello Dave,
Wavelab LE8 does not support the Mp3 Upgrade Patch. Are you sure you didn’t have Wavelab LE7 or Elements 7 or 8 installed? Wavelab Elements 7 and 8 included a 30 day trial of the Mp3 Encoder Patch. If that is the case you would need to purchase the patch. You can access it from our online shop at the following link.
http://www.steinberg.net/en/shop/buy_product/sku/500242444.html