Skeleton component not working

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I’d like to use skeleton to replace content when loading. but after try to implement it, the skeleton component is not working properly. the skeleton blink animation works properly but the skeleton block is not appear. For reference please see the image above.
This is my script:

<f7-list media-list v-if="!isRefresh"> <f7-list-item v-if="isRefresh" v-for="n in 3" :key="n" :class="skeleton-text skeleton-effect-blink" title="Full Name" subtitle="Position" text="Lorem ipsum dolor sit amet, consectetur adipisci interdum. " ></f7-list-item> </f7-list>