Make sure when you're in the update channel list, (Feed URL, Categories, Branding) to also go to the BOTTOM one, I think it's Preview & Publish, and there will be a button saying Publish or Update or something.
Kindof an undetailed workflow as one could easily add Categories or a new URL feed and click Save at the buttom, unaware they also need to goto the Preview & Publish page too. But likely that could be your problem, if not please post back.