Map not being displayed - Contacts related to Accounts

I am working through the Visualforce book on Mapping

Here’s a page that shows a list of contacts for an account, centered on the account’s address.
view sourceprint?
01<apex:page standardController="Account">
02
03  
05
06  <apex:pageBlock >
07    <apex:pageBlockSection title="Contacts For {! Account.Name }">
08
09     <apex:dataList value="{! Account.Contacts }" var="contact">
10       <apex:outputText value="{! contact.Name }" />
11     </apex:dataList>
12
13  <apex:map width="600px" height="400px" mapType="roadmap"
14    center="{!Account.BillingStreet},{!Account.BillingCity},{!Account.BillingState}">
15
16    <apex:repeat value="{! Account.Contacts }" var="contact">
17    <apex:mapMarker title="{! contact.Name }"
18       position="{!contact.MailingStreet},{!contact.MailingCity},{!contact.MailingState}"
19    />
20    </apex:repeat>
21
22  </apex:map>
23
24    </apex:pageBlockSection>
25  </apex:pageBlock>
26
27</apex:page>

and its suppose to create this map

User-added image