If your students are saying they can't post to discussions, or can't see where to post to discussions, there could be several possibilities.
Possibility #1: You do not have a topic for them to post to.
Students can only post to Discussion Topics- not forums. If you created only a forum, students can't post to it. Students cannot post in a forum. You will need to create a topic in the forum in order for students to post. Students post threads in topics.
Resolution: Create a topic in your forum for students to post to.
Possibility #2: Your forum is locked, or your topic is locked.
If you have locked the forum, or locked the topic, students will not be able to post.
Resolution: Edit the forum/topic and on the Properties tab select Unlock forum/topic or "Unlock forum for a specific date range" (and set the date appropriately to grant them access). Click Save and Close.
Possibility #3: Your forum is hidden, or your topic is hidden.
If you hid your forum or topic, students won't be able to see it to post to it.
Resolution: Edit the forum/topic, and on the Properties tab select "Forum is always visible" or "Forum is visible for a specific date range" (and set the date appropriately to grant them access). Click Save and Close.
Possibility #4: Group or Section Restrictions are preventing access to the topic.
Edit the forum or topic and click the Restrictions tab. Is the "Restrict this forum/topic to the following groups and sections" selected? If so, only the students in the group or section can see the forum or topic.
Resolution: Remove the group or section restrictions from the forum or topic. Or modify group or section restrictions. See the BOLT Help Course for more information.