Thank you for posting your query on Microsoft Q&A. From above query I could understand that you are following Protect your APIs with Defender for APIs and have enabled Defender for APIs plan but Defender for APIs is missing from the recommendations and instead you are getting Microsoft Defender for APIs should be enabled among recommendations.
Please do correct me by responding in the comments section if this is not the case.
This behavior is expected as After enabling Defender for APIs, onboarded APIs take up to 50 minutes to appear in the Recommendations tab.
You may try now, and the Defender for APIs should be available in recommendations.
Please "Accept the answer" (Yes), and share your feedback if the suggestion answers you’re your query. This will help us and others in the community as well.