There is a section which shows the reason for the same

Don't see a Start button?

If you don't see a blue 'Start Delta Exam' button above this text, you don't have access to this exam. There are several possible reasons for this:

• Perhaps, you haven't completed the prerequisites for this exam - see the Prerequisites tab below the image on the left-hand side to find out what you need to complete to access this exam.
• This content is only intended for Celonis Partner Certification holders who need to complete a Delta Exam in order to maintain the validity of their Certification - if you don't need to complete this Delta Exam, you won't be able to access it. Instead, check out our catalog to find content that's designed for you.
• You must be logged in to access this content.

If you believe you should have access to this content and none of the reasons above apply, please reach out to academy@celonis.com.

Basically send an email to academy@celonis.com.