Have you authorised your computer in the iTunes Store? And you need to accept the Terms and Conditions.
If this fails I would suggest reporting it Podcasts Support. Go to Podcaster Support and click the 'Contact Us' link at the bottom of the page.
If that fails the next step is to contact Apple Support: https://getsupport.apple.com/. Don't present this as a podcasting problem - they don't handle those and will refer you to Podcasts Support (or give you an inaccurate answer judging by some people's experience). Present the problem as being the inability to access Podcasts Support. It's also been suggested that getting them to look at your Apple ID may clear matters.