Podcasts are distributed via RSS. Each podcast producer hosts their own audio files. Therefore, the podcast producer may update the url of audio files or delete audio files, which is beyond our control.
Listen Notes is a podcast search engine, which indexes publicly accessible RSS-based podcasts. It's like Google, which indexes publicly accessible web pages.
It's possible that you click on some web pages from Google search results and find that those web pages are actually deleted.
Similarly, it's possible that you find some podcasts from Listen Notes and find that those podcast audio files are deleted and become unplayable.
Fix unplayable audio urls
On the Listen Notes website, you may encounter unplayable podcast audio:
You can help fix the potentially broken audio url - Go to EDIT tab of an episode page (Example) and put a valid audio url there:
You can find the valid audio url from the podcast's official website (if they do have such website) or check if they update the audio url in the rss feed. Listen Notes periodically check if podcasts update their rss feed or audio urls, but we can't do it timely enough.
Chrome browser issues
If you are using a desktop version Chrome browser with version newer than 80, then Chrome blocks an unsafe audio url (with http://, rather than https://) from playing. You can tell Chrome to allow playing such http:// audio urls on the Listen Notes website.
First, go to the Site settings for listennotes.com:
Then, change Insecure content to "Allow":
Finally, go to listennotes.com again and you should be able to play those http:// audio urls.