1inch swap API issue

I am trying to use 1inch swap API, but getting error most of the time. I’m trying to swap USDT to one custom token. The required allowance has already been provided.

I sometime get the response (even this has some issue, will highlight it below)
But for most of the time, Im getting cannot estimate error.

API URL: https://api.1inch.io/v4.0/56/swap?fromTokenAddress=0x55d398326f99059ff775485246999027b3197955&toTokenAddress=0xaf3889ba617ac973b358513d9031778d2bc783df&amount=1000000000000000000&fromAddress=0x06125e1457f833E29D5aebAaCdF8eED8A6Febaee&slippage=8

Error response:

{
    "statusCode": 400,
    "error": "Bad Request",
    "description": "cannot estimate",
    "meta": [],
    "requestId": "46c5abbb-347d-43d1-9c90-35ab8a220449"
}

And when getting the response, the value is always 0.

Response:

{
    "fromToken": {
        "symbol": "USDT",
        "name": "Tether USD",
        "decimals": 18,
        "address": "0x55d398326f99059ff775485246999027b3197955",
        "logoURI": "https://tokens.1inch.io/0xdac17f958d2ee523a2206206994597c13d831ec7.png"
    },
    "toToken": {
        "address": "0xaf3889ba617ac973b358513d9031778d2bc783df",
        "decimals": 9,
        "symbol": "SHIBIC",
        "name": "Shiba Inu Classic",
        "logoURI": "https://etherscan.io/images/main/empty-token.png",
        "isCustom": true
    },
    "toTokenAmount": "1502695685638969",
    "fromTokenAmount": "1000000000000000000",
    "protocols": [
        [
            [
                {
                    "name": "PANCAKESWAP_V2",
                    "part": 100,
                    "fromTokenAddress": "0x55d398326f99059ff775485246999027b3197955",
                    "toTokenAddress": "0xaf3889ba617ac973b358513d9031778d2bc783df"
                }
            ]
        ]
    ],
    "tx": {
        "from": "0x06125e1457f833E29D5aebAaCdF8eED8A6Febaee",
        "to": "0x1111111254fb6c44bac0bed2854e76f90643097d",
        "data": "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",
        "value": "0",         // THIS IS ALWAYS ZERO
        "gas": 1089735,
        "gasPrice": "15000000000"
    }
}

Can someone suggest me what exactly is the issue here?