p:fileUpload not working after rendered by p:ajax - ajax

Question

I´m getting confused why the component p:fileUpload doesn´t call the fileUploadListener once the component is shown by the p:ajax. If I put it outside the panelGrids or even remove them, works just fine.
What isn´t working:
<div class="pure-control-group">
<label for="mostraNoIndex">Slideshow</label>
<p:selectBooleanCheckbox value="#{destaqueCadastrarBean.d.apareceNoSlide}">
<p:ajax event="change" update="upload"></p:ajax>
</p:selectBooleanCheckbox>
</div>
<h:panelGrid id="upload">
<h:panelGrid rendered="#{destaqueCadastrarBean.d.apareceNoSlide}">
<div class="pure-control-group">
<label for="mostraNoIndex">Imagem</label>
<p:fileUpload fileUploadListener="#{destaqueCadastrarBean.handleFileUpload}" mode="advanced" dragDropSupport="true" sizeLimit="100000000000" fileLimit="1" allowTypes="/(\.|\/)(gif|jpe?g|png)$/" />
</div>
</h:panelGrid>
</h:panelGrid>
What works:
<div class="pure-control-group">
<label for="mostraNoIndex">Slideshow</label>
<p:selectBooleanCheckbox value="#{destaqueCadastrarBean.d.apareceNoSlide}">
</p:selectBooleanCheckbox>
</div>
<div class="pure-control-group">
<label for="mostraNoIndex">Imagem</label>
<h:fileUpload fileUploadListener="#{destaqueCadastrarBean.handleFileUpload}" mode="advanced" dragDropSupport="true" sizeLimit="100000000000" fileLimit="1" allowTypes="/(\.|\/)(gif|jpe?g|png)$/" />
</div>

Answer 1

Just found out a solution for it. The bean being called was RequestScoped, changed it to ViewScoped. I guess cause the bean was requested when the form loaded and p:fileUpload can only appears after the creation of the bean, the component couldn´t reach the bean. With view scope the bean is available for components that comes afterward. If someone has a more technical and clear explanation I would like to understand better.