iTunes not updating new episodes in Store

I can see no problem in the feed to cause this. The Store does sometimes seem to get 'stuck' and have a considerable delay in updating the occasional podcast. Usually it sorts itself out in the end, but it's pretty frustrating. You could try emailing Support, though I suspect you won't get much help, however nothing to lose by trying. Go to https://itunespodcasts.zendesk.com/hc/en-us/requests/new and click the disclosure triangle at the right of the 'Choose a topic' field - choose 'Other' and proceed from there.