@media (max-width: 767px) {

  /* контейнер кнопок */
  .simplecheckout-button-block-buttons {
    display: block !important;
    height: auto !important;
    min-height: 1px;
    overflow: visible !important;
    clear: both;
  }

  /* левый блок кнопки */
  .simplecheckout-button-left {
    display: block !important;
    float: none !important;
    width: 100%;
  }

  /* сама кнопка */
  #simplecheckout_button_confirm {
    display: block !important;
    visibility: visible !important;
    opacity: 1 !important;
    width: 100%;
  }

}

@media (max-width: 767px) {

  #button-confirm,
  #continue-button,
  #collapse-checkout-confirm input[type="submit"] {
    display: none !important;
  }

}