Error in plugin @nomiclabs/hardhat-etherscan: The contract verification failed. Reason: Fail - Unable to verify (solidity 0.8.4)

Question

I am newbie on solidity . trying to create NFT contract . I ve able to hardhat compile and deploy contract .

however during verify my contract with arguments and I am getting this error:

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

I am also importing Open Zeppelin contracts ERC721Enumerable and Ownable.

Here's my contract.sol

pragma solidity ^0.8.4;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";

contract TigerNft is ERC721Enumerable, Ownable {

    using SafeMath for uint256;
    string public FTP_PROVENANCE = "";
    uint256 public constant MAX_SUPPLY = 10000;
    uint256 public constant MAX_PUBLIC_MINT = 2;
    uint256 public constant MINT_PRICE = 28000000000000000; //0.028 ether;
    string private _baseTokenURI;

    uint256 public startingIndexBlock;
    uint256 public startingIndex;
    uint256 public REVEAL_TIMESTAMP;
    bool public saleIsActive = false;
    bool public isAllowListActive = false;
    mapping(address => uint256) public _allowList;

    constructor() ERC721("FortuneTigersPunk", "FTP") {
        _baseTokenURI = "ipfs://QmNm3JHSGhBgL5D5sBov2kjAtxDKEoC9SF1Rq81Tqt52jp/";
   
    }
     modifier callerIsUser() {
        require(tx.origin == msg.sender, "Caller is contract");
        _;
    }
      /* Set provenance once it's calculated 
     This function is to update the hash of the image containing all the apes. This image is generated and stored outside of the blockchain */

    function setProvenanceHash(string memory provenanceHash) public onlyOwner
    {
        FTP_PROVENANCE = provenanceHash;
    }
    
     function setBaseURI(string memory baseURI) public onlyOwner {
        setBaseURI(baseURI);
    }
    function setIsAllowListActive(bool _isAllowListActive) external onlyOwner {
        isAllowListActive = _isAllowListActive;
    }

    function setAllowList(address[] calldata addresses, uint8 numAllowedToMint) external onlyOwner {
        for (uint256 i = 0; i < addresses.length; i++) {
            _allowList[addresses[i]] = numAllowedToMint;
        }
    }
    function numAvailableToMint(address addr) external view returns (uint256) {
        return _allowList[addr];
    }
    function mintAllowList(uint8 numberOfTokens) external payable{
    uint256 ts = totalSupply();
    require(isAllowListActive, "Allow list is not active");
    require(numberOfTokens <= _allowList[msg.sender], "Exceeded max available to purchase");
    require(ts + numberOfTokens <= MAX_SUPPLY, "Purchase would exceed max tokens");
    require(MINT_PRICE.mul(numberOfTokens) <= msg.value, "Ether value sent is not correct");

        _allowList[msg.sender] -= numberOfTokens;
        for (uint256 i = 0; i < numberOfTokens; i++) {
            _safeMint(msg.sender, ts + i);
       }
   }

    function setSaleState() public onlyOwner {
        saleIsActive = !saleIsActive;
    }
    function mint(uint numberOfTokens) public payable {
        uint256 ts = totalSupply();
        require(saleIsActive, "Sale must be active to mint tokens");
        require(numberOfTokens <= MAX_PUBLIC_MINT, "Exceeded max token purchase");
        require(ts + numberOfTokens <= MAX_SUPPLY, "Purchase would exceed max tokens");
        require(MINT_PRICE.mul(numberOfTokens) <= msg.value, "Ether value sent is not correct");

        for (uint i = 0; i < numberOfTokens; i++) {
            if (totalSupply() < MAX_SUPPLY) {
            _safeMint(msg.sender, ts + i);
           }
        }
    // If we haven't set the starting index and this is either 1) the last saleable token or 2) the first token to be sold after
        // the end of pre-sale, set the starting index block
     if (startingIndexBlock == 0 && (totalSupply() == MAX_SUPPLY || block.timestamp >= REVEAL_TIMESTAMP)) {
            startingIndexBlock = block.number;
      } 
    }
    function withdraw() public onlyOwner {
        uint balance = address(this).balance;
        payable(msg.sender).transfer(balance);
    }
}

Here's my deploy.ts

import { ethers} from "hardhat"

const main = async () =>{
  const FTPFactory = await ethers.getContractFactory("TigerNft") ;
  const FTPContract = await FTPFactory.deploy();
  console.log(`NFT address: ${FTPContract.address}`);
}
  main().catch((error)=> {
    console.error(error);
    process.exitCode =1;
  });

Here's my hardhat.config.ts

import * as dotenv from "dotenv";
import { HardhatUserConfig, task } from "hardhat/config";
import "@nomiclabs/hardhat-etherscan";
import "@nomiclabs/hardhat-waffle";
import "@nomiclabs/hardhat-ethers";
import "@typechain/hardhat";
import "hardhat-gas-reporter";

dotenv.config();

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);
  }
});

const config: HardhatUserConfig = {
  solidity: "0.8.4",
  networks: {
    rinkeby: {
      url: process.env.RINKEBY_URL,
      accounts:
        process.env.PRIVATE_KEY !== undefined ? [process.env.PRIVATE_KEY] : [],
    },
  },
  gasReporter: {
    enabled: process.env.REPORT_GAS !== undefined,
    currency: "USD",
  },
  etherscan: {
    apiKey: process.env.ETHERSCAN_API_KEY,
  },
};
export default config;

Answer 1

I fixed this error try to put const FTPContract = await FTPFactory.deploy("FortuneTigersPunk", "FTP");

compile, deploy again and verify.

Answer 2

i try import factories from typechain and its working fine now.

However i still dont know it it failed at 1st stage without import factories.

import { ethers} from "hardhat"
import { TigerNft__factory} from "../typechain-types";

const main = async () =>{
  // const FTPFactory = await ethers.getContractFactory("TigerNft") ;
  const FTPFactory = await ethers.getContractFactory("TigerNft") as TigerNft__factory;
  const FTPContract = await FTPFactory.deploy();
  // const FTPContract = await FTPFactory.deploy("FortuneTigersPunk", "FTP");
  // const MAXNFT = (await ethers.getContractFactory("MaxNFT")) as MaxNFT__factory;
  //const nft = await MAXNFT.deploy();

 // console.log(`NFT address: ${nft.address}`);
  console.log(`NFT address: ${FTPContract.address}`);
}
  main().catch((error)=> {
    console.error(error);
    process.exitCode =1;
  });