I need to disable the selection of days on flatpickr.
From the documentation, I see that to do this, you need to pass the days via the "disable" parameter. I get the days from an API call, with response:

"2021-01-21","2021-01-16"

When i try with

 var req = new XMLHttpRequest();
req.onreadystatechange = function() {
    if (req.readyState === 4) {
        var response = req.responseText;
        console.log(response);
        flatpickr("#myID", {
        disable: [response],
        dateFormat: "Y-m-d",
}
    );
    }
};
req.open('GET', 'https://www.peradev.it/api/getGiorni.php?id=1');
req.send(null);

only the first day works, the second one is not disabled. What i'm wrong?