Not a claim. YouTube will put ads on videos regardless of whether you are monetized... and that is a good thing. While YT gets a lion's share of the revenue collected across the platform the more money they make the better off we all are.Sounds like it may be a copyright claim on that video. I would check in the analytics to make sure theirs not a claim on it and if it is, change the song or whatever content is being claimed.
Hello Stacy,
What you suggest is not possible because all my content is made by me and I use the YouTube sound library, also in YouTube Studio appears that my channel is free of any copyright infringement and in the future it can monetize without problems, the situation is how Damon mentioned, YouTube can place ads where it sees fit. Thank you for your concern.