I'm not sure of specific 'tony ignores peter fanfiction' off the top of my head. But you can try searching on fanfiction platforms like Archive of Our Own. There are likely to be many works there that might match what you're looking for.
Peter may try to get Tony's attention back. He could show off his own skills or achievements in an attempt to remind Tony of his value. For example, he might go on a solo mission and do an amazing job, hoping that Tony will notice him again.
Well, it could be that Tony is focused on protecting Morgan and sees Peter as capable of handling himself, which leads to him ignoring Peter. And Peter might get hurt in a dangerous situation that he wasn't fully prepared for.
Often, they emphasize the relationship between Peter and Tony. It could be a mentor - mentee relationship like in many stories where Tony imparts his wisdom and experience to Peter. For example, in some fanfics, Tony helps Peter understand his powers better.
Perhaps in the fanfic's storyline, Tony is facing a lot of pressure himself, like threats from powerful villains or issues within the Avengers. Peter's actions, whether they are mistakes or just inconvenient timing, could be the straw that breaks the camel's back for Tony, causing him to yell at Peter.
Peter could be a character with some heroic or special qualities. He might be a young man with a big heart. Morgan could be a young girl, perhaps a student at the school. They could have a special bond, like an older brother - like figure (Peter) and a younger sister - like figure (Morgan).
Another possibility is that Doctor Strange could rescue Peter. He has powerful magic and the ability to travel through different dimensions. He might sense that Peter is in danger through his magic and use his powers to find Dark Tony's lair and free Peter. Strange could also use his magic to fight off Dark Tony if he tries to stop the rescue.
Family is also a theme sometimes. They can be seen as a sort of surrogate family to each other. For example, Tony may act like a father figure to Peter. Additionally, the theme of heroism and growing into one's role as a hero is often explored. Peter is learning from Tony how to be a better hero, and Tony is also learning from Peter in some ways, like how to have more hope and innocence in the face of danger.