The latest episode in the feed is that of 24th November, and this appears in the iTunes Store in iTunes on a Mac and when subscribing in iTunes, so everything is normal so far.
I'm not in a position to check in the iOS Podcasts App. I have an idea that it works from the iTunes Store rather than the feed, though I'm not sure about that, but either way it should be showing that episode.
The first thing to do would be to check on another iOS device and see whether the episodes are missing there too. If you have a friend or contact who can do this for you that would be simplest; you could also ask in the iPhone forum where someone who can check it and possibly advise if their is a problem may be able to assist you.