enter image description here

<div id="modal" class="zoom-anim-dialog modal-block modal-block-primary mfp-hide" style="overflow:hidden;">
    <div class="form-group row pb-2">
        <select data-plugin-selectTwo class="form-control populate" data-plugin-options='{ "minimumInputLength": 6 }'></select>
    </div>
</div>

When use on modal this problem