As mentioned in Techcommunity article - Welcome, Microsoft Learn Student Ambassadors - "Earn a free certification by completing steps like a Microsoft Learn path, writing a blog post, or recording a video tutorial that helps others learn from your passion for technology. "
Having mentioned that, for issues with your Learn Profile, Certifications, and Exams (including registration and scheduling), please reach out on the Microsoft Certification forums:
https://trainingsupport.microsoft.com/en-us/mcp
For more info: Microsoft Certification help