I am using a button that opens a modal, when the screen is maximized it works ok but when it is minimized or a mobile view is used, the screen is greyed out, but the modal does not appear, how could I fix it?

I leave the code and some images.

Modal when the screen is maximized :

Modal when the screen is minimized:

Modal

<div class="modal fade" id="livestream_scanner" tabindex="-1" role="dialog" aria-labelledby="exampleModalLongTitle" aria-hidden="true">
        <div class="modal-dialog" role="document">
            <div class="modal-content">
                <div class="modal-header">
                    <h5 class="modal-title" id="exampleModalLongTitle">Modal title</h5>
                    <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                        <span aria-hidden="true">&times;</span>
                    </button>
                </div>
                <div class="modal-body">
                    ...
                </div>
                <div class="modal-footer">
             <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
                    <button type="button" class="btn btn-primary">Save changes</button>
                </div>
            </div>
        </div>
    </div>