As I cannot find it by searching it would appear that your podcast has been removed from the Store. Subscribers are accessing your feed directly - the Store is not involved once they have subscribed - which is why they are continuing to see it.
There appear to be no technical problems with the feed. Other possible reasons for removal (and I'm not accusing you of any of these) include strong or sexual language when the 'explicit' tag is not set to 'yes', or at any time in titles, subtitles or summaries; unacceptable sexual content; misuse of Apple's trademarks; and breach of copyright.
Most of these would seem inapplicable; I haven't listened to any of it and wouldn't know anyway if there were swearing.
If you don't have any of these issues it might even have been removed in error - not common, but not unheard of either. You could try emailing Support at podcasts 'at' apple.com and asking why it was removed, though I can't promise you will get a helpful answer.