试图通过 pancakeswap 路由器合约出售但不能

Question

我正在尝试从 pancakeswap 路由器调用函数“SwapExactTokensForETHSupportingFeeOnTransferTokens”，但无论我尝试什么，每次交易都会被还原，错误代码为“Transferfrom failed”。我要出售的代币已被手动批准。

如果有人想帮助我解决这个问题，这里是函数

def sell():
    pancakeswap2_txn = pcscontract.functions.swapExactTokensForETHSupportingFeeOnTransferTokens(
            2000000000000000,0, #2000000000000000 = equals to 0.002BNB
            [sellcontractaddress,wbnb],
            sender_address,
            (int(time.time()) + 10000)
        ).buildTransaction({
            'from': sender_address,
            'gasPrice': w3.toWei(str(gwei), 'gwei'),
            'value': 0,
            'gas': 50000,
            'nonce': w3.eth.get_transaction_count(sender_address),
        })

    signed_txn = w3.eth.account.sign_transaction(pancakeswap2_txn, private_key=privatekey)
    tx_token = w3.eth.send_raw_transaction(signed_txn.rawTransaction)
    print(f"Sold {symbol}: " + w3.toHex(tx_token))
sell()