ERC721 signature verification (cryptography contracts)

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:computer: Environment

environment:

Hardhat, solidity compiler version 0.8.1, ethers js, windows 10, node version 12.13.1, npm 7.8.0

:memo:Details

I am creating a mintable erc721 token that requires a new minter to verify a signature generated by an existing minter following this workshop repository https://github.com/OpenZeppelin/workshops/tree/master/06-nft-merkle-drop.
the test failed with the error “only_existing_minter” in the contract required check.

:1234: Code to reproduce

solidity code:

constructor()

        

        ERC721("My NFT", "MyNFT")

        EIP712("MYNFT", "1.0.0")

    {}

    function _hash(

        address newArtist,

        uint256 nonce

    ) public view returns (bytes32) {

        return

           _hashTypedDataV4(keccak256(abi.encode(

            keccak256("Register(address newArtist,uint256 nonce)"),

            newArtist,

            nonce

        )));

    }

    function _verify(bytes32 digest, bytes memory signature)

        private

        pure

        returns (address)

    {

        return ECDSA.recover(digest, signature);

    }

    // serve as the verifyNewMinter function
   // signature is generated by existing minter (wallet address of new minter and the nonce, usually 1 as the message object)
// msgSender is the new minter 
    function register(

        bytes calldata signature

    ) external {

        require(nonces[_msgSender()]==0, "user_exist");

        address signer =

            _verify(_hash(_msgSender(), nonces[_msgSender()]++), signature);

        require(signer != address(0), "address_0");

        require(isMinter[signer], "only_existing_minter");

        _addMinter(_msgSender(), payable(signer));

    }

javascript code:

   const overrides = {

  gasLimit: 9999999,

};

   const domain = {

      name: "MYNFT",

      version: "1.0.0",

      chainId: 1,

      verifyingContract: myNft.address,

    };

const types = {

      Register: [

        { name: "newArtist", type: "address" },

        { name: "nonce", type: "uint256" },

      ],

    };
    const nonce = 1;
    const values = { other1.address, nonce };

    const signature = await other0._signTypedData(domain, types, values);

    console.log("Signature: ", signature);
    await myNft.connect(other1).register(signature, overrides);

// other0 is an existing minter