Button not rendered after upload file - jsf

Question

I want to render a button after upload a file, I have selectOneMenuto chose options, when I upload the file with the first option, the button didn't rendered but it rendered after I chose the second option.
ManagedBean.java
private boolean viewImport;
public boolean isViewImport() {
return viewImport;
}
public void setViewImport(boolean viewImport) {
this.viewImport = viewImport;
}
public void processFiless(FileUploadEvent event) {
setViewImport(true);
}
import.xhtml
<ui:composition template="./../../../../template.xhtml">
<ui:define name="content">
<h:form id="form1" prependId="false">
<p:growl id="messages"/>
<h1><h:outputText value="#{customerData.importBatchTitle}" /></h1>
<div class="formSection">
<p:panel header="#{app['import.fileSelectionForm']}" id="importFile" toggleable="true" toggleSpeed="300">
<h:graphicImage styleClass="formimg" url="/images/orange/fleche2.gif"/><h:outputText value="#{app['import.contract.parameter.primal']}" />
<h:selectOneMenu value="#{customerData.parameterType}">
<f:selectItems value="#{customerData.parameterTypeItems}" />
<p:ajax actionListener="#{customerData.selectionParameterType}" event="change" update="form1"/>
</h:selectOneMenu>
<br/>
<br/>
<h:panelGroup rendered="#{customerData.viewUpload}">
<p:fileUpload update="form1" fileUploadListener="#{customerData.processFiless}" >
<p:ajaxStatus>
<f:facet name="start">
<h:graphicImage value="/images/ajaxloading.gif" />
</f:facet>
<f:facet name="complete" >
<h:outputText value="" />
</f:facet>
</p:ajaxStatus>
</p:fileUpload>
</h:panelGroup>
</p:panel>
<br/>
<f:subview id="modifyCustt" rendered="#{customerData.viewImport}">
<p:commandButton value="ok"></p:commandButton>
</f:subview>
</div>
</h:form>
</ui:define>
</ui:composition>