All the posts I've found relating to fixing this iTunes error message are old and the fixes no longer work, so I would appreciate some updated advice on fixing this issue.
When I click 'subscribe' on a podcast (The Retrievals) in the Apple Store, I receive the error message: "Your request produced an error. [newNullResponse]"
There is also a popup window: "There was a temporary problem completing your request. The iTunes Store is temporarily unavailable. Please try again later."
I have tried over the last three days with multiple podcasts and always receive the same error message. I have logged out of my iTunes account, restarted computer and logged back into iTunes and still get the same error message. I have tried updating my payment details (previous recommended fix), though it's a paypal account and there's nothing really to update.
I am using iTunes version 12.9.5.5 on an iMac using macOS Mojave 10.14.6.
Would appreciate any assistance.