Every story needs conflict. It's got to have at least one kind of problem that the main character(s) spend the story trying to solve.
Though almost always, there's more than one conflict going on. As there are different aspects of life, a character may have problems from multiple areas in their "world." Like for example, a character could be trying to solve a bullying problem at school while trying to deal with a family issue at home, and maybe also trying to remedy their own feelings of insecurity.
A handful of problems keeps a character on their toes--which is good for a story.
Here are a few ideas for sources of conflict:
Finances. A shortage of money can mean losing a lifestyle or moving away from a beloved area; and a sudden gain of money (while it has its charming benefits) can attract unwanted attention or threaten to make the protagonist shallow.
A figure/secret from the past. A mistake the character made long ago that could cause serious damage to their life and/or their reputation; an old enemy who's come to rock the boat.
Visitors. A mysterious stranger, a new student, the crazy uncle . . .
Troublemakers. Someone who likes to play games with people and their lives. People like this aren't common in real life, but they can make things a little more interesting in fiction.
Relationships. Arguments with friends, rivalry between coworkers, having issues with the boyfriend/girlfriend, etc.
Family: Why can't they just get along with each other? Does the protagonist verbally battle their sibling or their parents? Is there some kind of competition for attention?
Someone else having a problem: What if the best friend got dumped by her boyfriend and started clinging to the protagonist like a wet rag? What if the protagonist's sibling got in trouble with the law?
Death: It touches everyone. And it is
always horrible to go through.
Changing society: These are especially useful in historical novels. How would the main character react to the world around them becoming totally different? Maybe they would have trouble adjusting to changes.
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