Post launch of new Pega academy existing learning courses are inaccessible. In new academy it is mentioned to use previous app but opening the URL always shows page not found. Below is the link provided in certifications details page.
PLEASE NOTE: The Decisioning Consultant certification exam has not yet been updated to cover the material in the new Mission. If you are interested in taking the current exam, please complete the Decisioning Consultant course in the previous Pega Academy application. The updated exam will be available in July 2020.