search and replace on google slide refuse to work

I'm trying to replace placeholder Text with text from form or var on Google Slides using Google Script

everything looks like it working but when I open the new google slides the placeholder are not changed. Thanks.

function project(){

var projectname = '666'
var category = '12345'
var subtitle = '12345'
var excerpt = '12345'

 
 //PP-Slides template file, and you get it by ID
 var file = DriveApp.getFileById('fileID');
 //We can make a copy of the template, name it, and optionally tell it what folder to live in
//file.makeCopy will return a Google Drive file object
var folder = DriveApp.getFolderById('folderid')
var copy = file.makeCopy(projectname + '-' + "Project", folder).getId();
var Slides = SlidesApp.openById(copy).getSlides();

Slides.forEach(slide => requests = [{
      replaceAllText: {
        containsText: {
          text: '{{subtitle}}',
          matchCase: true
        },
        replaceText: projectname
      }
}]);

Logger.log(copy);
Logger.log(Slides);
console.log(projectname);
}