Thank you for posting your query Microsoft Q&A, from above description I could understand that you have been looking for advisory on Microsoft defender for cloud showing security score as Not available.
Please do correct me by responding in the comments section if this is not the ask.
Secure Score is calculated based on the security recommendations that are generated by Microsoft Defender for Cloud.
When you turn on Defender for Cloud in a subscription, the Microsoft cloud security benchmark (MCSB) standard is applied by default in the subscription. Assessment of resources in scope against the MCSB standard begins. The MCSB issues recommendations based on assessment findings.
If you Microsoft defender for cloud plan expires or is not renewed, then MCSB is not applied hence no security recommendation, or secure score is issued.
Please "Accept the answer (Yes)" and "share your feedback ". This will help us and others in the community as well.
Thanks,
Akshay Kaushik