sermon Cast setup?

I'm using SermonSpeaker 4.5.x (I can't see the last version number). I'm assuming it's the latest one because it normally updates itself. I'm on Joomla 2.5.11.

You could check the exact version number in your extension manager

But it's strange anyway. If you look at the sourcecode of your empty feed, you see a generator tag stating "SermonSpeaker 4.3". If you indeed have installed SermonSpeaker 4.5.x it should be "SermonSpeaker 4.5".
This generator tag is created in the layout file itself found in /components/com_sermonspeaker/views/feed/tmpl/default.php.

Apparently this file (and maybe others as well) wasn't properly replaced during the update for some reason.

Can you try installing SermonSpeaker 4.5.4 again over your existing installation (without uninstalling first!)?. Please watch for any errors during installation. Try again after that.
If that doesn't help, you maybe want to copy the files manually using FTP.

It all makes sense now. The problem was caused by the fact I have overridden SermonSpeaker's component in my template and I had forgotten to update the default.php file for the feed view. It all works now.
Thanks.

God bless!

Aye, that makes sense