Ethers.js approve 'invalid address or ENS name'

Trying to swap exact tokens for tokens using ethers.js - for some reason, I can't get it to work past the approve stage.

Here's a little code snippet:

const provider = new ethers.providers.WebSocketProvider(provider_address)
const wallet = ethers.Wallet.fromMnemonic(mnemonic)
const account = wallet.connect(provider)

const erc20_ABI =
    [
        {
            "constant": true,
            "inputs": [],
            "name": "name",
            "outputs": [
                {
                    "name": "",
                    "type": "string"
                }
            ],
            "payable": false,
            "stateMutability": "view",
            "type": "function"
        },
        {
            "constant": false,
            "inputs": [
                {
                    "name": "_spender",
                    "type": "address"
                },
                {
                    "name": "_value",
                    "type": "uint256"
                }
            ],
            "name": "approve",
            "outputs": [
                {
                    "name": "",
                    "type": "bool"
                }
            ],
            "payable": false,
            "stateMutability": "nonpayable",
            "type": "function"
        },
        {
            "constant": true,
            "inputs": [],
            "name": "totalSupply",
            "outputs": [
                {
                    "name": "",
                    "type": "uint256"
                }
            ],
            "payable": false,
            "stateMutability": "view",
            "type": "function"
        },
        {
            "constant": false,
            "inputs": [
                {
                    "name": "_from",
                    "type": "address"
                },
                {
                    "name": "_to",
                    "type": "address"
                },
                {
                    "name": "_value",
                    "type": "uint256"
                }
            ],
            "name": "transferFrom",
            "outputs": [
                {
                    "name": "",
                    "type": "bool"
                }
            ],
            "payable": false,
            "stateMutability": "nonpayable",
            "type": "function"
        },
        {
            "constant": true,
            "inputs": [],
            "name": "decimals",
            "outputs": [
                {
                    "name": "",
                    "type": "uint8"
                }
            ],
            "payable": false,
            "stateMutability": "view",
            "type": "function"
        },
        {
            "constant": true,
            "inputs": [
                {
                    "name": "_owner",
                    "type": "address"
                }
            ],
            "name": "balanceOf",
            "outputs": [
                {
                    "name": "balance",
                    "type": "uint256"
                }
            ],
            "payable": false,
            "stateMutability": "view",
            "type": "function"
        },
        {
            "constant": true,
            "inputs": [],
            "name": "symbol",
            "outputs": [
                {
                    "name": "",
                    "type": "string"
                }
            ],
            "payable": false,
            "stateMutability": "view",
            "type": "function"
        },
        {
            "constant": false,
            "inputs": [
                {
                    "name": "_to",
                    "type": "address"
                },
                {
                    "name": "_value",
                    "type": "uint256"
                }
            ],
            "name": "transfer",
            "outputs": [
                {
                    "name": "",
                    "type": "bool"
                }
            ],
            "payable": false,
            "stateMutability": "nonpayable",
            "type": "function"
        },
        {
            "constant": true,
            "inputs": [
                {
                    "name": "_owner",
                    "type": "address"
                },
                {
                    "name": "_spender",
                    "type": "address"
                }
            ],
            "name": "allowance",
            "outputs": [
                {
                    "name": "",
                    "type": "uint256"
                }
            ],
            "payable": false,
            "stateMutability": "view",
            "type": "function"
        },
        {
            "payable": true,
            "stateMutability": "payable",
            "type": "fallback"
        },
        {
            "anonymous": false,
            "inputs": [
                {
                    "indexed": true,
                    "name": "owner",
                    "type": "address"
                },
                {
                    "indexed": true,
                    "name": "spender",
                    "type": "address"
                },
                {
                    "indexed": false,
                    "name": "value",
                    "type": "uint256"
                }
            ],
            "name": "Approval",
            "type": "event"
        },
        {
            "anonymous": false,
            "inputs": [
                {
                    "indexed": true,
                    "name": "from",
                    "type": "address"
                },
                {
                    "indexed": true,
                    "name": "to",
                    "type": "address"
                },
                {
                    "indexed": false,
                    "name": "value",
                    "type": "uint256"
                }
            ],
            "name": "Transfer",
            "type": "event"
        }
    ]

const STG_address = '0x2F6F07CDcf3588944Bf4C42aC74ff24bF56e7590'
const STG_contract = new ethers.Contract(
    STG_address,
    erc20_ABI,
    account
)

const init = async () => {
    console.log('before contract approve')

    //
    let receipt = await STG_contract.approve(account, ethers.utils.parseUnits('1000.0', 18), { gasLimit: 100000, gasPrice: 5e9 });

    console.log('await contract approve happened')
}

init()

Running the above results in a 'invalid address or ENS name' error.

If I change the let receipt... part to:

let receipt = await STG_contract.approve('my actual wallet address', ethers.utils.parseUnits('1000.0', 18), { gasLimit: 100000, gasPrice: 5e9 });

Then the code executes, however the contract approve never resolves

What am I doing wrong?

Thanks