Hello,
Thank you for posting in Q&A forum.
Normally, once you complete the challenge and register for your corporate email, you will receive a free Microsoft certification exam coupon within the next week. If it has been more than a week but has not been received, please check your spam folder to ensure that your email has not misclassified the email. If you still haven't received it, please contact the Microsoft Certification Support team for further assistance, please refer to
Results in Microsoft Credentials - Training, Certification, and Program Support
Hope this answer can help you well.
Best regards,
Jill Zhou