Feed in Apple Podcast Subscribe not working

Dear Podcasters,

I try to make use of the Subscribe Icon/ Link in the Player. I configured the services, but the feed link
always results in the error: ‘Podcast cannot be added because the server or feed cannot be found.’

The link I feed the Player´s config is https://mywebsite/feed/podcast/

The show is up on Apple Podcasts with one episode. Player is working great. The feed link is exactly the one generated in the Publisher’s backend!

Would anyone have an idea what I am missing?

Cheers and thank you!