Metadata integration with OpenSea


I have an issue with metadata. I am using Openzeppelin ERC 721 preset, complied and deployed the contract via Remix to Rinkeby and want to see it in testnet on OpenSea.
I established a IPFS folder with metadata files 0, 1 etc (created with Windows Notepad saved as .json, uploaded to IPFS and then renamed so that the “.json” is not there); next, I minted token with tokenURI “ipfs://-CID-/0”; however I cannot see this on a testnet validate check which throws me an error: “InvalidTokenUrlResponseException: Invalid JSON response for URL:”. I am using OpenSea metadata standard.
When I open the ipfs link, it shows the file fine.

Can you please help me how to resolve this one?