No dump

Hello, I have followed the procedure to make a prebuildlayout. So I’ve inserted the 2 lines in wp-config, but when I go to a page and display the source I see nowhere the dump with php array :

After you’ve enabled debug mode, you’ll get a full dump of your page’s content as a PHP array. To do this, view the HTML source of a page builder page you’ve already created. Then search for the following string Page Builder Data. You’ll see a standard HTML comment with the PHP for your page. Copy this array, we’ll be using it shortly.

Do you have a solution?