If you have a student account and your Dashboard shows all topics as locked, these could be for a few reasons.
The most common reason is that you have not yet graduated from the Training Field. To graduate from the Training Field you need to earn 30 XP in the Dialogue Space linked to the Learning Dojo.
As soon as you earn 30 XP in the Training Field, you get your first Dialogue Title and you unlock all learning topics on the Ultimate Dialogue Adventure.
If topics are locked and you have graduated from the Training Field, this might be because you have already started a topic. You can only go through one learning topic at a time. To start a new topic you can either complete the topic you have already started, or you can cancel the progress for the current topic and start a new one.