Google Base Feed does not work

Does anyone have experience with the Google Base Feed ?
I enabled it, uploaded the latest category list, added Google categories and webshop categories, but nothing is showing when I go to the feed (only one line).

<?xml version="1.0" encoding="UTF-8" ?><rss version="2.0" xmlns:g="http://base.google.com/ns/1.0"> <channel> <title>WEBSHOP</title> <description>WEBSHOP</description> <link>http://www.webshop.com/</link> </channel></rss>

What am I doing wrong ?