Session id is not getting generated for Anon user

As a bug report this needs much more detail and steps to reproduce. If there is custom code we must see all of it to identify the bug in Drupal.

@cilefen, Please find below custom code which we are using to generate anon user session ID. But once we clear drupal cache it is not generating again.

function custom_page_attachments(array &$page) {
page['#attached']['session_id'] = \Drupal::service('session_manager')->getId();
}

A common reason for this kind of thing is missing cache contexts → in custom code.

No additional info provided so I'm closing this, if anyone is able to reproduce it please update the issue summary with steps.