Hello Joao

Thank you for your purchase.

When working with JSON format please note: Currently, wpDataTables accepts this, and only this, format of JSON (see example): a one-level array of same-structured objects where each object will be parsed as a row, and each field inside of the object as a cell. If your software does not return this format, you would need to prepare, as an example some PHP adapter to return one of the formats that wpDataTables would accept.

So it needs to be rather simple, like this:

[
    {
        "Column1": "Data1",
        "Column2": "Data2",
        "Column3": "Data3",
        "Column4": "Data4"
    },
    {
        "Column1": "Data1-1",
        "Column2": "Data2-1",
        "Column3": "Data3-1",
        "Column4": "Data4-1"
    }
]

And so on.

Best regards.