Unfortunately, according to Microsoft's certification renewal policy, since your Microsoft Certified: Power Platform Solution Architect Expert certification expired on June 15, 2024, you won't be able to renew it through the free online assessment on Microsoft Learn.
Here are some helpful resources:
- Microsoft Certification Renewal: https://learn.microsoft.com/en-us/credentials/certifications/renew-your-microsoft-certification
- Renew your Microsoft Certification - FAQ: https://learn.microsoft.com/en-us/credentials/certifications/renew-your-microsoft-certification