backingBean doens't receive commandButton action - primefaces

Question

Im using a rendered commandButton and other button to save input data, But the backing bean doens't receive input from view. I tried all proposition in this post[post]but still doens't work, any help, thanks in advance
here is a part of the code:
<ui:define name="content">
<div class=" marginA">
<div class="row">
<ul class="E">
<p:dataList value="#{userManager.user.diplomas}" var="d">
<h:panelGrid columns="2">
<h:panelGrid columns="1" cellpadding="2">
<h:outputText value="#{d.title}"/>
<h:outputText value="in #{d.dateDiploma} }"/>
</h:panelGrid>
</h:panelGrid>
</p:dataList>
</ul>
<p:commandButton action="#{userManager.switchEdit(true)}"
icon="ui-icon-plus"
type="submit"
immediate="true"
update="add"
ajax="true">
</p:commandButton>
<h:panelGrid columns="4" cellpadding="5" >
<h:outputLabel for="diploma" value="Diploma:"/>
<p:inputText id="diploma"
value="#{userManager.diploma.title}"
required="true">
</p:inputText>
<p:commandButton value="add"
actionListener="#{userManager.addDiploma()}"
imediate="true"
ajax="true"
process="#this"
icon="ui-icon-check" />
</h:panelGrid>
</div>
</div>