A common flaw in a story is the one-conversation conflict. That's a problem that can be solved with one honest conversation between the characters.
Some novels, particularly romances, are driven by this conflict through the whole story because the two main characters simply won't ask questions or tell each other the truth.
This kind of conflict is based on misunderstanding, not on important emotional issues. It reflects badly on characters by making them appear immature, and, for most readers, the promised happily ever after appears unlikely with two such shallow characters.
It also reflects badly on the writer who hasn't bothered to work on the plot and conflict.
A one conversation conflict can work well in a scene, or as a means to hold back a valuable clue in a mystery for a short period, but it should only be used judiciously and not as a major part of the conflict structure of the novel.
Examples of a bad one conversation conflict:
"Oh, she's your younger sister, and that's why you were hugging her."
"So you were taking dance lessons for our wedding, not dating someone else."
"You're a vampire, and you were out getting a snack? That's a relief. I thought you weren't home at night because you were sleeping with someone else!"