Clicking the 'subscribe' button in the iTunes Store brings up the Dropbox feed, so the redirect is working, but unlike when subscribing the Store does not show the second episode of December 16th. I can't see any problem with it in the feed, so probably the Store has simply got into one of its sticky patches. I'm afraid there isn't really anything you can do except wait for it to catch up.
Being puzzled by this - particularly as the episode which hasn't appeared is only a few hours later than the one which has - I've had another look at the feed. There is nothing in the feed itself to cause the problem; but it does occur to me that there is one other possible explanation.
We've had issues in other podcasts occasionally where the iTunes application would read and subscribe to a feed perfectly well, but the Store wouldn't - I've never seen a convincing explanation about this but it looks as if some servers don't react properly to requests coming from the Store.
Dropbox is, to be honest, not really a good place to use for website or podcast hosting. It does work fine with the iTunes application, as we've seen, but I suppose it may be a possibility that it's not handling requests from the Store properly. That would explain the symptoms - I'm assuming that you added the new-feed-url tag at the same time as you added the second episode of December 16th. The Store is looking for the Dropbox feed, because of the redirect in the old feed, but if it's not getting a response then it will continue to display the cached information from the old feed.
The Subscribe button works because although it's sending the application to the old feed, there is an immediate redirection there. (If you subscribe manually to the old feed it immediately changes to the new one).
In the event that my guess is correct, you will have to start by asking Dropbox whether they can advise. If you can't get any satisfaction there, and the Store still doesn't update, you are in a bit of a bind since you can't add another redirection tag to be read by the Store.
You would have to move the feed and the episodes to another server, add the redirection tag to the DropBox feed to redirect the iTunes Application yet again, and then email podcasts 'at' apple.com and ask them to move the Store to the new URL.
As I say I'm running on guesswork here, but if you don't get an update in the Store then it may be your only way to proceed.
Roger, thanks so much for taking the time to look into this in so much detail. What you say makes perfect sense. I have tried to contact dropbox in the past and they don;t really do support, but I've seen similar comments so I think that is it. I will find a better home for my podcast and then email apple and ask them to point to it. Do you have any suggestions for inexpensive hosts? I guess I can still leave the actual audio on dropbox, since the store accepted a feed before that referenced the audio.
Just to finish this thread off. The solution I found was to use Google's feedburner service for hosting the podcast feed and keep the content on dropbox. As Roger deduced in the posts above, iTunes store doesn't like a podcast feed from dropbox. Fortunately, it turns out that if the new-feed-url tag points to what iTunes store thinks is an invalid feed, it reverts to the ogirinal feed. So what I did was to create a Google feedburner podcast whose "Original Feed" resides on dropbox. I then went to my original podcast feed and used the new-feed-url tag to point to my Google feedburner feed. iTunes store likes this. I can now make changes in my xml feed on dropbox which is picked up by the Google feedburner feed and thence to the iTunes store. Everything updated within one hour.
This also means that I can move my source in the future and change the "Original Feed" in feedburner without having to make any iTunes store specific changes.
Source XML hosted where you wante -> Feedburner -> iTunes Store
does this mean that you can host on dropbox?
i've been doing dropbox>tumblr>feedburner>itunes, and this just doesn't work.
can you please elaborate on the above?
Apologies, but this is sending me a little insane at the mo and I'm pulling out what little hair I have left!
My plan is basically to be able to host my podcast on dropbox (I've already got a pro account) and get it on itunes etc so that it can be subscribable.
No one that knows anything about podcasting would recommend dropbox as a podcast host.
It is just plain a bad solution for podcast hosting and anyone recommending it is giving bad advice.
If your reason for using dropbox is to save money - then use internet archive. But dropbox is not designed for or intentended for use as a podcast host.
If money is not the reason - then go and find a good podcast host and get a service designed specifically for podcasters. The Price between libsyn.com and Dropbox pro is minimal for example.
If any of those 100 potential listeners are on an iOS device - then they are SOL as dropbox does not support byte range requests.
And there is a good chance you will not get the podcast into iTunes.
To put it simply find another solution - Dropbox is not meant for podcasting.
You will notice on this forum and others people having issues with Dropbox. Just don't do it.