I’ve just tested the lite version and the rss works fine on this end.
What’s the permalink structure you’re using there?
Does it still happen when testing in the default WordPress theme?
And does it still work with all other plugins disabled?
If it does then reactivate each one, one at a time and keep testing until the issue comes back again. When it does that should let us know where a potential conflict lays. If this occurs then please let us know which plugin or theme our plugin conflicts with.