Troubles with comments Elgg 3.1.3

Hi everyone,

I am using the latest elgg release. But the comment box is not available under posts. So users cannot add comments.

For instance when a user add a Blog post and publish it, the comment box is not available at the bottom.  So users cannot add comments on their own post. Moreover we have the same behavior when other users are connected. So finally users cannot add comments.

But only administrators can add comments. When the administrator is connected, the comment box is available under the posts.

How can I handle this ?