This has been a problem for some people. You must have a payment method registered in Apple Music/iTunes: make sure your computer is authorised to play purchases (Apple Music or iTunes menu Account>Authorisations>Authorise this Computer). Then try logging in at https://podcastsconnect.apple.com
If this fails I would suggest reporting it Podcasts Support. Go to Apple Podcasts for Creators 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.