One obstacle could be that Harry doesn't have all the information he needs. He might not know exactly who has his money or how much is missing. Without this crucial information, it's really hard for him to take the right steps to get his money back. And there could be some emotional obstacles too. Maybe he is too afraid to confront the person who has his money because he is worried about ruining their relationship.
Perhaps there are some legal barriers. For example, the person who has his money might have some legal justifications for keeping it, at least on the surface.
In the fanfic, it could be that Harry has a very smart friend who helps him come up with a clever plan. For example, they might find a loophole in a contract that the person who has Harry's money was using to keep it. So, by exploiting this loophole, Harry is able to legally get his money back. Another possibility is that Harry has some special skills or powers in the story that he uses to his advantage. He could use his charm to persuade the person who owes him money or his intelligence to outwit them in a negotiation.
Well, she might face the obstacle of Percy's changed circumstances. He could be in a new place or situation that makes it difficult for her to reach him. Also, their past issues could be an obstacle. If they had a big fight before they split, those unresolved problems might make it hard for Annabeth to convince Percy to come back. And there could be social pressure in the fanfiction world, like friends or groups who think they're better off apart.
One challenge could be resistance from the existing authority. There might be some teachers or administrators who don't want to give up their power easily. They may see Harry as too young or inexperienced.
Hermione could be the one. With her vast knowledge of the wizarding laws and her sharp intellect, she might dig up some old regulations that prove Harry's right to his money. She would then fight tooth and nail in the wizarding courts or against the goblins at Gringotts to get his money back.
Maybe he discovers some legal loophole in the wizarding world's financial system that allows him to reclaim his inheritance. For example, if there was some improper handling of his family's vault by the goblins at Gringotts, he could use that as a basis to demand his money back.
There could also be external factors. For example, there might be a prophecy or some sort of danger that keeps Percy away from Annabeth. He might be so focused on dealing with this external threat that he doesn't have time or energy to think about getting back together with her.
One challenge could be the lack of the traditional focus for his magic. Without a wand, he might struggle to direct his magic precisely. For example, when he tries to cast a simple levitation spell, he may end up making objects fly out of control.
Sirius has to figure out how to give Harry a normal childhood while also training him in magic. He can't just let Harry be unprepared for the wizarding world, but he also doesn't want to push him too hard. Also, he may face financial difficulties. Raising a child isn't cheap, and he might have to find ways to earn money while also taking care of Harry.
The Dementors are a huge challenge. Their presence alone can drain his happiness and will to escape. He has to find a way to avoid them or protect himself from their effects.
One challenge could be dealing with his cousin's non - magical mindset. Since Harry is a wizard and his cousin is likely a Muggle, the cousin may not understand or believe in magic at first. This could lead to a lot of misunderstandings. Another challenge might be protecting his cousin from the wizarding world's dangers without scaring him too much. For example, there could be dark wizards or magical creatures that pose a threat.