I assume 'available' means you see the related list in the Configure > Related Lists slush bucket, but when you add it to the Selected records and Save, you do not see it on the form, not to be confused with adding fields to a form via Configure > Form Layout. On every Related List in Configure > List Control there is a checkbox Omit if empty that will hide the Related List if it is empty. The way to see if this has been checked, since you can't see the Related List is sys_ui_list_control.list in the left nav, then open the record for this related list.
