Your channel may be lacking context or info about the creative value you’re adding to make the content unique. Check out these best practices and after making changes, you can always re-apply again in 30 days: https://yt.be/help/reused-content …
If you upload content from multiple sources, or reupload/repurpose someone else’s existing content (ie “reuse content”) then you won’t be eligible for YPP. Check out the FAQs and best practices here: https://yt.be/help/reused-content …