Agregué algo de estilo en .title y .description en mi hoja de estilo para mi componente de test , pero no estoy seguro de por qué no se aplicó el estilo.

 const test = Vue.component("test", { template: `<div class="test"> <span class="title">{{title}}</span> <div class="description">{{description}}</div> </div>`, props: { id: Number, title: String, description: String, }, });

HolaMundo.vue

 <template> <div id="hello"> <test v-for="item in steps" :key="item.id" :id="item.id" :title="item.title" :description="item.description" /> </div> </template> <script> import Vue from "vue"; const test = Vue.component("test", { template: `<div class="test"> <span class="title">{{title}}</span> <div class="description">{{description}}</div> </div>`, props: { id: Number, title: String, description: String, }, }); export default { components: { test, }, data() { return { steps: [ { id: 1, title: "What is Lorem Ipsum?", description: "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.", }, ], }; }, }; </script> <style scoped lang="scss"> #hello { display: flex; flex-direction: column; .test { /* style applied */ text-align: left; margin-top: 10px; .title { /* style not applied */ font-size: 50px; color: orange; } .description { /* style not applied */ font-size: 10px; line-height: 12px; color: red; } } } </style>

Códigosycaja:
https://codesandbox.io/s/amazing-flower-rcvob?file=/src/components/HelloWorld.vue