Hey, it sounds like a bug I ran into also, when I refreshed the live preview page, it told me that I didn't have permission to access the data, and when I went to the profile section and back, it worked.
We are working on a fix for that bug - I suspect the root cause is that the authentication token doesn't get loaded fast enough on that preview page which is our fault. You should however be immediately be able to view the data you have purchased in any canvas or in your core/streams listing page once the transaction has confirmed on the blockchain.
Other things to remember:
- Make sure the ETH address you used to purchase the product exists in your 'Ethereum Address' on the Profile page.
- Wait until the transaction is confirmed on the blockchain. Metamask confirmation or Etherscan is your best source of truth here ATM.
Sorry about the frustration - we are pushing updates frequently now so I hope these sorts of bugs will be gone soon! Let me know if I can help you out with anything else.