How to keep v-data-table header when sorting columns?

Question

I am new to VueJS. I currently have trouble with my v-data-table. Every time I try to sort a table column, the header will be disappeared. After researching, I used 'fixed-header' prop and set the height for the table. However, it didn't work. How can prevent the header disappear?

Here is my code

   <VBTable
      top
      :auto-hide-footer="false"
      :server-paging="true"
      :loading="loading"
      :columns="headers"
      fixed-header
      :page.sync="internalPagination.page"
      :options.sync="internalPagination"
      :items="customers"
      :total="total"
      height="800"
      :show-select="false"
      :class="[{ 'empty-table': isEmpty, 'loading-table': loading }]"

    >