shipping_rates.json returning different results in Cart Vs Checkout

[thesozostudio]

Please note: uninstalling apps and using default themes has no impact

Suddenly the shipping rates request via the Shopify API is not returning expected results in the Cart page. (But it does load all the rates in the Checkout page which is obviously not using the API, but Shopify checkout logic.)

For the postal code provided (M4K 2H8), it should provide Standard Delivery ($15.00) and Local Delivery ($7.00). The local delivery logic is based on passing M* as a wildcard (and other postal codes) to allow local delivery as per the screenshots.

However the Shopify API only returns the following when the request is submitted to https://www.topknotliving.com/cart/shipping_rates.json:

{
    "shipping_rates": [
        {
            "name": "Standard",
            "presentment_name": "Standard",
            "code": "Standard",
            "price": "15.00",
            "markup": "0.00",
            "source": "shopify",
            "delivery_date": null,
            "delivery_range": null,
            "delivery_days": [
                3,
                9
            ],
            "compare_price": null,
            "phone_required": false,
            "currency": "CAD",
            "carrier_identifier": null,
            "delivery_category": null,
            "using_merchant_account": null,
            "carrier_service_id": null,
            "description": null,
            "additional_data": null,
            "incoterm": null,
            "api_client_id": null,
            "requested_fulfillment_service_id": null,
            "shipment_options": null,
            "charge_items": null,
            "has_restrictions": null,
            "rating_classification": null,
            "accepts_instructions": false
        }
    ]
}

The form data submitted is

shipping_address%5Bzip%5D=M4K+2H8&shipping_address%5Bcountry%5D=Canada&shipping_address%5Bprovince%5D=Ontario

It used to work where both shipping options were provided in the response in the Cart, but now doesn't work. Why? How do we resolve this? It's affecting conversiobs.