How to solve this error?

Question

function approveBurn(address nft_cont_address,uint256 _tokenId) public {
  ERC721 tokenContract = ERC721(nft_cont_address);
  // approve the contract to burn the token
  tokenContract.approve(address(this), _tokenId);
}

Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending? Returned error: {"jsonrpc":"2.0","error":"execution reverted: ERC721: approve caller is not token owner or approved for all","id":8066513221942198}

Why am I getting this error and how to solve this?

Answer 1

The sender for this function in the NFT contract will be the contract through which you are calling the function. Is your contract owner of the tokens, if not then please share the contract. If no then you need to directly call the approve function from your wallet, not from another contract, coz the contract becomes msg.sender when calling another contract.