comment form no visibile at the end of the articles

Good morning,
I saw several topics about the one I opened, but some of them are closed, whereby I’m opening the new one.
Given that in my blog is enabled the option to allow comment to the posts, I tried the solution given by Ismael and someone else in the old topics, namely:

a) in the page.php (after </main>) I added:
//wordpress function that loads the comments template “comments.php”
comments_template();

b) in the functions.php (at the end of the file) I addedd:

dd_filter(‘comments_open’, function() {
return true;
}, 9999);

c) in /includes/helper-assets.php I uncommented the line add_filter( ‘comments_open’, ‘av_comments_on_builder_posts_required’, 10, 2 );

No one of the solution above worked for me, may you be so kind to help me?
Thank you and have nice day
Carlo