I have been tracking down a problem with a podcast published by Podlove not playing via the Google Podcast app, and I thought for documentation purposes I should post here.
Google apparently made a change that requires the podcast content to be served over HTTPS not HTTP (redirects don’t count as served over http), so you need a valid HTTPS certificate for your webserver. I suspect LetsEncrypt free certs would work, but I have not tested that.
One of my favorite 3d Printing podcasts is published with Podlove (“The Meltzone” podcast) was not playing on Google Podcasts app, so I started digging around.