Verify/Publish Smart Contract on Etherscan Rinkeby

Question

I am attempting to Verify and Publish a smart contract that I have deployed to the rinkeby network using hardhat and hardhat-etherscan. When I am running the verify script I am getting an error.

I run the following commands

npx hardhat clean 
npx hardhat verify --network rinkeby 0xDDeE39Ae632760906d273B450493405Dc3C455Fe "ipfs://QmX6MjxS5NsEFGe9WtKCskf5fhuifFvZ9Xi12tTBYPjEiH"

After running the script above I get the below error.

Compiling 17 files with 0.8.4
Compilation finished successfully
Compiling 1 file with 0.8.4
Successfully submitted source code for contract
contracts/NFTCollectible.sol:NFTCollectible at 0xDDeE39Ae632760906d273B450493405Dc3C455Fe
for verification on Etherscan. Waiting for verification result...

We tried verifying your contract NFTCollectible without including any unrelated one, but it failed. Trying again with the full solc input used to compile and deploy it. This means that unrelated contracts may be displayed on Etherscan...

Successfully submitted source code for contract contracts/NFTCollectible.sol:NFTCollectible at 0xDDeE39Ae632760906d273B450493405Dc3C455Fe for verification on Etherscan. Waiting for verification result...

Error in plugin @nomiclabs/hardhat-etherscan: The contract verification failed.
Reason: Fail - Unable to verify

hardhat.config.js

require("@nomiclabs/hardhat-waffle");
require("@nomiclabs/hardhat-etherscan");
require('dotenv').config();

const { API_URL, PRIVATE_KEY, ETHERSCAN_API } = process.env;

// This is a sample Hardhat task. To learn how to create your own go to
// https://hardhat.org/guides/create-task.html
task("accounts", "Prints the list of accounts", async (taskArgs, hre) => {
  const accounts = await hre.ethers.getSigners();

  for (const account of accounts) {
    console.log(account.address);
  }
});

// You need to export an object to set up your config
// Go to https://hardhat.org/config/ to learn more

/**
 * @type import('hardhat/config').HardhatUserConfig
 */
module.exports = {
  solidity: "0.8.4",
  defaultNetwork: "rinkeby",
  networks: {
    rinkeby: {
      url: API_URL,
      accounts: [PRIVATE_KEY]
    }
  },
  etherscan: {
    apiKey: ETHERSCAN_API
  }
};

My smart contract included several imports from openzepplin.

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/utils/Counters.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";

contract NFTCollectible is ERC721Enumerable, Ownable {
    using SafeMath for uint256;
    using Counters for Counters.Counter;

    Counters.Counter private _tokenIds;

    uint256 public constant MAX_SUPPLY = 100;
    uint256 public constant PRICE = 0.01 ether;
    uint256 public constant MAX_PER_MINT = 5;

    string public baseTokenURI;

    constructor(string memory baseURI) ERC721("NFT Collectible", "NFTC") {
        setBaseURI(baseURI);
    }

    function reserveNFTs() public onlyOwner {
        uint256 totalMinted = _tokenIds.current();
        require(totalMinted.add(10) < MAX_SUPPLY, "Not enough NFTs");
        for (uint256 i = 0; i < 10; i++) {
            _mintSingleNFT();
        }
    }

function _baseURI() internal view virtual override returns (string memory) {
    return baseTokenURI;
}

function setBaseURI(string memory _baseTokenURI) public onlyOwner {
    baseTokenURI = _baseTokenURI;
}

function mintNFTs(uint256 _count) public payable {
    uint256 totalMinted = _tokenIds.current();
    require(totalMinted.add(_count) <= MAX_SUPPLY, "Not enough NFTs!");
    require(
        _count > 0 && _count <= MAX_PER_MINT,
        "Cannot mint specified number of NFTs."
    );
    require(
        msg.value >= PRICE.mul(_count),
        "Not enough ether to purchase NFTs."
    );
    for (uint256 i = 0; i < _count; i++) {
        _mintSingleNFT();
    }
}

function _mintSingleNFT() private {
    uint256 newTokenID = _tokenIds.current();
    _safeMint(msg.sender, newTokenID);
    _tokenIds.increment();
}

function tokensOfOwner(address _owner)
    external
    view
    returns (uint256[] memory)
{
    uint256 tokenCount = balanceOf(_owner);
    uint256[] memory tokensId = new uint256[](tokenCount);
    for (uint256 i = 0; i < tokenCount; i++) {
        tokensId[i] = tokenOfOwnerByIndex(_owner, i);
    }

    return tokensId;
}

function withdraw() public payable onlyOwner {
    uint256 balance = address(this).balance;
    require(balance > 0, "No ether left to withdraw");
    (bool success, ) = (msg.sender).call{value: balance}("");
    require(success, "Transfer failed.");
}

}

Answer 1

I just had this problem and solved it by realizing that my constructor arguments did not match with what I originally deployed the contract with. For you it is possible this:

npx hardhat verify --network rinkeby 0xDDeE39Ae632760906d273B450493405Dc3C455Fe "ipfs://QmX6MjxS5NsEFGe9WtKCskf5fhuifFvZ9Xi12tTBYPjEiH"

should actually be: npx hardhat verify --network rinkeby 0xDDeE39Ae632760906d273B450493405Dc3C455Fe "QmX6MjxS5NsEFGe9WtKCskf5fhuifFvZ9Xi12tTBYPjEiH" with the ipfs:// removed if you did not originally include it when you initially deployed the contract.

I would redeploy it and double check the parameters used when deploying are identical to the ones used when verifying.