hmmmm... spent hours to get the issue solved... for the sake of the childrens aka students ^_^
well, hope we are facing same problem...
first, you must make sure the students have permission to do the action eg. reply post/news
second
if you have set the course setting for
group mode = Separate groups
then
in the course you MUST create a group and assign the students into that group, so that the students can reply or post(depends on the permission setting)
to create a group:
navigate to the course, under Setting -> Course Administration-> Users-> Groups
then you should see the list of groups created (for the particular course)
now, press the button "create group", fill up the details, save
highlight the group, press the button Add/remove users and add the potential users.
now, create a NEW post/news and log in as a students account to check whether the 'reply' button is available
for old post, i believe it will remain the same (no reply button) as it has been set to 'all participant' but not the group.
good luck ^_^