Apple Podcasts - cannot link subscriptions to multiple publications

There seems to be an issue right now linking Apple Podcasts app to two separate unrelated podcast subscriptions I have (the subscriptions were not purchased via Apple)

1. I click the button on the podcast that says 'Already a subscriber?", to link my subscription so I can listen to subscriber episodes.
2. An incognito window opens in my web browser, asking me to log in with the login for that particular subscriber publication.
3. I log in correctly, and then Apple Podcasts opens up in the browser window (not in the app) and I see a message 'This page cannot be found'.
4. Going back to the podcast app, the subscription has not been linked and I cannot listen to subscriber episodes.

This is happening for two different, unrelated subscriber podcasts, so it isn't an issue with the subscription. One month ago I successfully linked a different podcast, so it seems to be a new issue.