WordPress piotnetforms plugin how to run Jquery code after form submission

Solution:

From the link you gave us, it seems that your submit button has an event listener which has e.preventDefault(). It means submit event never fires! You can change the event you’re listening for, to click event.

jQuery(function ($) {
  $('.piotnetforms-button').on('click', function () {
    alert("submit button clicked!");
  })
})