Metadata file shows up via direct IPFS URI in browser - but not displayed as metadata of NFT item at OpenSea

Anyone have experience of this issue - I have successfully added an image and a json file to my node and pinned them. I’ve set the token URI in my smart contract for NFTs. The items are directly accessible in a browser - both the json file and the .png file. However, despite the URI being correct, the data does not display in an OpenSea listing for the item at Rinkeby testnet. I guess this is a factor of OpenSea cache or display and not something at IPFS side - esp. as I can access directly my node files - node is up and running. Any ideas appreciated.