Podcasts not showing up

Subscribing to podcasts has been working great in the past, but recently it stopped working.

If I subscribe to a new podcast via the (German) iTunes store on OS X (10.10.4) using iTunes (12.2.0.145) no episodes show up and most of the times not even the artwork/cover-photo.

How can I fix this? I already tried deleting my iTunes folder and starting fresh.