Have you gone through the approval process? The accepted use cases are very restrictive, and specifically do not support allowing you to access more than 20 of your own posts.
"I want to display hashtag content and public content on my website."
"This use case is not supported. We do not approve the public_content
permission for one-off projects such as displaying hashtag based
content on your website. As alternative solution, you can show your own
Instagram content, or find a company that offers this type of service
(content discover, moderation, and display)."
