I'm trying to create a pop-up browswer in GAS. What I wanna do here is post some value to my local api and get response from it. My code below doesn't work as I meant to and it's stuck in the screen in the picture. Api doesn't get any request meaning post is not working successfully. Any advice will be appreciated.

  if (cell_tick == true) {
    var tick_row = cell_pos.getRow();
    var date = new Date();
    sheet.getRange(tick_row, date_column).setValue(date).setNumberFormat('yyyy/MM/dd H:mm:ss'); 
    
    openTab()
    function openTab() {
    var js = "<script language='JavaScript'>\
    function openWindow()\
    {\
    myWindow = window.open('about:blank','theWindow','width=400,height=400');\
    }\
    </script>\
    <form method='POST' name='myForm' action='http://127.0.0.1:5000/' target='theWindow'>\
    <input type='text'>\
    <input type='button' onERASETHISClick='openWindow(); document.myForm.submit()' value='Open and after submit'>\
    </form>;\
    "
    var html = HtmlService.createHtmlOutput(js)
      //.setHeight(10)
      //.setWidth(100);
    SpreadsheetApp.getUi().showModalDialog(html, 'Now loading.');
    }
  }