I can not download tables as excel

The thing is simple, I want to export a table of primefaces to .xlsx however at the moment of pressing the button that should do it, I get the following exception:

java.lang.ClassNotFoundException: org.apache.poi.ss.usermodel.RichTextString

It's as if it will not detect apache poi, however I do have it installed.

This is the image of my view:

The code of my view:

<h:form prependId="false" id="listadoUsuarios">

        <div class="row">
            <div class="col s2">
                <h:commandLink class="btn">
                    Exportaaaaar
                    <p:dataExporter type="xls" target="listadoUsuarios" fileName="ok" pageOnly="true"/>
                </h:commandLink>
            </div>
        </div>

        <div class="row">
            <div class="col s12">
                <p:dataTable value="#{userController.allUsers}" var="u">
                    <p:column headerText="Nombre" filterMatchMode="contains" filterBy="#{u.name}" sortBy="#{u.name}">
                        <h:outputText value="#{u.name}"/>
                    </p:column>
                    <p:column headerText="Email" filterMatchMode="contains" filterBy="#{u.email}" sortBy="#{u.email}">
                        <h:outputText value="#{u.email}"/>
                    </p:column>
                    <p:column headerText="Teléfono" filterMatchMode="contains" filterBy="#{u.phone}" sortBy="#{u.phone}">
                        <h:outputText value="#{u.phone}"/>
                    </p:column>
                </p:dataTable>
            </div>
        </div>
    </h:form>

The code of my pom.xml on the web where I have apache-poi:

<dependency>
        <groupId>com.lowagie</groupId>
        <artifactId>itext</artifactId>
        <version>2.1.0</version>
    </dependency>

    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi</artifactId>
        <version>3.2-FINAL</version>
    </dependency>

    <dependency>  
        <groupId>org.primefaces</groupId>  
        <artifactId>primefaces</artifactId>  
        <version>6.0</version>  
    </dependency>  

I hope you can help me achieve it: /