Do you ever have learners in Moodle saying that they can’t post in a forum?
What would students be unable to post to a forum?
The most common reason is that the forum is actually an Announcements forum.
This is a special forum for news and general announcements which is automatically created for each course, and which by default only Teachers (and administrators) can post in.
As a teacher, you need to ensure that students understand they cannot reply to posts, or make new posts in an Announcements forum.
However, to create a standard forum in which students can post, turn editing on for the course, click the ‘Add an activity or resource’ link, and then choose Forum.
On rare occassions, students may be looking at a forum set to Groups, but they are not actually in a Group. They will therefore see a message “Adding discussions to this forum requires group membership“.
In this case, either add the Student to a Group, or change the Group Mode to ‘No Groups’. Obviously you need to think about the impact of the second change before you do this.