Not able to extract xml value using XSLT

The XML i'm using has multiple ROWS, i need to check value of one ROW and extract other ROW values. But for some reason i'm not able to succeed. Can you pls help.

PFB XSLT code

<?xml version="1.0" encoding="UTF-8"?>

<!--

XSL_ShapeMap.xsl

Abstract - The following XSL file is a stylesheet that
creates an HTML table of Shape Summary information
based on a Visio VDX file. This stylesheet supports the 
output on the Solution Design Hardware Table report.


-->

<xsl:stylesheet version="1.0" 
xmlns:xsl="http://ift.tt/tCZ8VR" 
xmlns:my="http://ift.tt/1uHbDwD"
xmlns:vis="http://ift.tt/1qlnOZi"
xmlns:r="http://ift.tt/1bA4cfb">
<xsl:template match="/">
    <table border="1" cellpadding="0" cellspacing="0" 
        style="BORDER-COLLAPSE: collapse" 
        bordercolor="#111111" width="100%">

        <!-- Display the column names. -->

        <tr>
            <td width="10%" bgcolor="#c6d9f1">
                <p style="text-align:center; font:bold 10pt Arial; 
                    MARGIN-TOP: 3px; MARGIN-BOTTOM: 3px;
                    MARGIN-LEFT: 3px">
                    Environment
                </p>
            </td>
            <td width="10%" bgcolor="#c6d9f1">
                <p style="text-align:center; font:bold 10pt Arial; 
                    MARGIN-TOP: 3px; MARGIN-BOTTOM: 3px;
                    MARGIN-LEFT: 3px">
                    Location
                </p>
            </td>

        </tr>

        <!-- Apply the template for displaying 
             the rows. -->

        <xsl:apply-templates select="my:PageContents" />


    </table>
</xsl:template> 



 <xsl:template match="my:Shapes">



    <xsl:for-each select="//my:Shape/my:Section/my:Row[@N='SBB_Class']">


    <!-- Apply a template for each shape that isn't
         a Dynamic Connector. The shape's information
         will display as a row of the table. -->

    <tr>
            <td bgcolor="#ffffff">
                <p style="font:normal 10pt Tahoma; 
                    MARGIN-TOP: 3px; MARGIN-BOTTOM: 3px; 
                    MARGIN-LEFT: 3px">


                        <xsl:if test="//my:Shape/my:Section/my:Row[@N='Environment']">



                        <xsl:value-of select= "@N" />
                    </xsl:if>



                </p>
            </td>
            <td width="66%" bgcolor="#ebdbed">
                <p id="idLastModifiedDate" style=
                    "font:normal 10pt Tahoma; 
                    MARGIN-TOP: 3px; MARGIN-BOTTOM: 3px;
                    MARGIN-LEFT: 3px">
                    <xsl:choose>
                        <xsl:when test="/my:PageContents/my:Shapes/my:Shape">

                            <xsl:value-of select= "@Name"   />

                        </xsl:when>

                        <xsl:otherwise>
                            (No value found)
                        </xsl:otherwise>
                    </xsl:choose>   



                </p>
            </td>
        </tr>
    </xsl:for-each>

</xsl:template> 

</xsl:stylesheet>

In the XML there are multiple ROWs under Shape, I need read all the shapes and if the shape has "SBB_Class" then i need to extract value of that row and fields of other rows as well(values presend in Cell of each Rows). PFB XML

  <?xml version="1.0" encoding="utf-8" ?> 
<PageContents xmlns="http://ift.tt/1uHbDwD" xmlns:r="http://ift.tt/1bA4cfb" xml:space="preserve">
 <Shapes>
<Shape ID="3" NameU="Existing Service" Name="Existing Service" Type="Group" LineStyle="6" FillStyle="6" TextStyle="6" UniqueID="{1E5E586C-0702-486D-AB90-8F678CE9E949}">
  <Cell N="PinX" V="3.385826771653544" /> 
  <Cell N="PinY" V="4.035433070866141" /> 
  <Cell N="Width" V="0.866141732283463" /> 
 <Cell N="Height" V="0.5905511811023612" /> 
 <Cell N="LocPinX" V="0.4330708661417315" F="Width*0.5" /> 
 <Cell N="LocPinY" V="0.2952755905511806" F="Height*0.5" /> 
 <Cell N="Angle" V="0" /> 
 <Cell N="FlipX" V="0" /> 
 <Cell N="FlipY" V="0" /> 
  <Cell N="ResizeMode" V="0" /> 
 <Cell N="EventDblClick" V="0" F="RUNMACRO("TAF___Visio_Template.NewMacros.ShapeDataMacro")" /> 
 <Cell N="EventDrop" V="0" F="RUNMACRO("TaxonomySelectorMacro(12)")" /> 
 <Cell N="ObjType" V="8" /> 
 <Section N="User">
 <Row N="SBB_Name">
  <Cell N="Value" V="Existing Service" U="STR" F="Prop.SBB_Name" /> 
  <Cell N="Prompt" V="RRRR" /> 
  </Row>
 <Row N="Short_Name">
  <Cell N="Value" V="0" /> 
  <Cell N="Prompt" V="NNNN" /> 
  </Row>
 <Row N="Proposed_SBB_Name">
 <Cell N="Value" V="0" /> 
  <Cell N="Prompt" V="WNNN" /> 
  </Row>
 <Row N="SBB_ID">
 <Cell N="Value" V="ES001" U="STR" F="Prop.SBB_ID" /> 
 <Cell N="Prompt" V="NNNN" /> 
 </Row>
 <Row N="SBB_Class">
 <Cell N="Value" V="Existing Service" U="STR" F="Prop.SBB_Class" /> 
 <Cell N="Prompt" V="NNNN" /> 
 </Row>
 <Row N="SBB_Type">
 <Cell N="Value" V="Existing Service" U="STR" F="Prop.SBB_Type" /> 
  <Cell N="Prompt" V="RRRR" /> 
  </Row>
 <Row N="Environment">
 <Cell N="Value" V="Development" U="STR" F="Prop.Environment" /> 
 <Cell N="Prompt" V="WWRR" /> 
 </Row>
 <Row N="Service_Model_Name">
 <Cell N="Value" V="0" /> 
 <Cell N="Prompt" V="WWWR" /> 
 </Row>