By reading the F.A.Q. section of the training course I can see that you have three attempts to pass the final exam, so if you do not get the required score after using all attempts, the exam will be locked. Also, at the end of this section, there is information about how to request for help, if you have a question that is not listed.
As explained there, I would use the tab "Messages" tab to send a message to "Denodo Training", so they will evaluate your situation and they will back to you with more information.
Hope this helps!