gistfile1.txt

<?xml version='1.0' encoding='UTF-8'?>
<methodCall>
  <methodName>DataService.query</methodName>
  <params>
    <param>
      <value><string></string></value>
    </param>
    <param>
      <value><string>DataFormField</string></value>
    </param>
    <param>
      <value><int>100</int></value>
    </param>
    <param>
      <value><int>0</int></value>
    </param>
    <param>
      <value><struct>
        <member><name>FormId</name>
          <value><string>-4</string></value>
        </member>
      </struct></value>
    </param>
    <param>
      <value>
        <array>
          <data>
            
              <value><string>Id</string></value>
            
              <value><string>DataType</string></value>
            
              <value><string>Name</string></value>
            
              <value><string>Label</string></value>
            
              <value><string>Values</string></value>
            
          </data>
        </array>
      </value>
    </param>
    <param>
      <value><string></string></value>
    </param>
    <param>
      <value><boolean>0</boolean></value>
    </param>
  </params>
</methodCall>



<?xml version="1.0" encoding="UTF-8"?>
<methodResponse>
    <params>
        <param>
            <value>
                <array>
                    <data>
                        <value>
                            <struct>
                                <member>
                                    <name>Label</name>
                                    <value>Final Opportunity Amount</value>
                                </member>
                                <member>
                                    <name>DataType</name>
                                    <value>
                                        <i4>3</i4>
                                    </value>
                                </member>
                                <member>
                                    <name>Id</name>
                                    <value>
                                        <i4>109</i4>
                                    </value>
                                </member>
                                <member>
                                    <name>Name</name>
                                    <value>FinalOpportunityAmount</value>
                                </member>
                            </struct>
                        </value>
                        <value>
                            <struct>
                                <member>
                                    <name>Label</name>
                                    <value>Expected First Payment</value>
                                </member>
                                <member>
                                    <name>DataType</name>
                                    <value>
                                        <i4>3</i4>
                                    </value>
                                </member>
                                <member>
                                    <name>Id</name>
                                    <value>
                                        <i4>111</i4>
                                    </value>
                                </member>
                                <member>
                                    <name>Name</name>
                                    <value>ExpectedFirstPayment</value>
                                </member>
                            </struct>
                        </value>
                        <value>
                            <struct>
                                <member>
                                    <name>Label</name>
                                    <value>Close %</value>
                                </member>
                                <member>
                                    <name>DataType</name>
                                    <value>
                                        <i4>4</i4>
                                    </value>
                                </member>
                                <member>
                                    <name>Id</name>
                                    <value>
                                        <i4>113</i4>
                                    </value>
                                </member>
                                <member>
                                    <name>Name</name>
                                    <value>Close</value>
                                </member>
                            </struct>
                        </value>
                        <value>
                            <struct>
                                <member>
                                    <name>Label</name>
                                    <value>Opportunity Type</value>
                                </member>
                                <member>
                                    <name>Values</name>
                                    <value>
MRR
ORR
Projects</value>
                                </member>
                                <member>
                                    <name>DataType</name>
                                    <value>
                                        <i4>21</i4>
                                    </value>
                                </member>
                                <member>
                                    <name>Id</name>
                                    <value>
                                        <i4>160</i4>
                                    </value>
                                </member>
                                <member>
                                    <name>Name</name>
                                    <value>OpportunityType</value>
                                </member>
                            </struct>
                        </value>
                    </data>
                </array>
            </value>
        </param>
    </params>
</methodResponse>



<?xml version='1.0' encoding='UTF-8'?>
<methodCall>
  <methodName>DataService.query</methodName>
  <params>
    <param>
      <value><string></string></value>
    </param>
    <param>
      <value><string>Lead</string></value>
    </param>
    <param>
      <value><int>100</int></value>
    </param>
    <param>
      <value><int>0</int></value>
    </param>
    <param>
      <value><struct>
        <member><name>LastUpdated</name>
          <value><string>%</string></value>
        </member>
      </struct></value>
    </param>
    <param>
      <value>
        <array>
          <data>
            
              <value><string>Id</string></value>
            
              <value><string>OpportunityTitle</string></value>
            
              <value><string>ContactID</string></value>
            
              <value><string>AffiliateId</string></value>
            
              <value><string>UserID</string></value>
            
              <value><string>StageID</string></value>
            
              <value><string>StatusID</string></value>
            
              <value><string>Leadsource</string></value>
            
              <value><string>Objection</string></value>
            
              <value><string>ProjectedRevenueLow</string></value>
            
              <value><string>ProjectedRevenueHigh</string></value>
            
              <value><string>OpportunityNotes</string></value>
            
              <value><string>DateCreated</string></value>
            
              <value><string>LastUpdated</string></value>
            
              <value><string>LastUpdatedBy</string></value>
            
              <value><string>CreatedBy</string></value>
            
              <value><string>EstimatedCloseDate</string></value>
            
              <value><string>NextActionDate</string></value>
            
              <value><string>NextActionNotes</string></value>
            
              <value><string>_FinalOpportunityAmount</string></value>
            
              <value><string>_ExpectedFirstPayment</string></value>
            
              <value><string>_Close</string></value>
            
              <value><string>_OpportunityType</string></value>
            
          </data>
        </array>
      </value>
    </param>
    <param>
      <value><string>LastUpdated</string></value>
    </param>
    <param>
      <value><boolean>0</boolean></value>
    </param>
  </params>
</methodCall>



<?xml version="1.0" encoding="UTF-8"?>
<methodResponse>
    <fault>
        <value>
            <struct>
                <member>
                    <name>faultCode</name>
                    <value>
                        <i4>10</i4>
                    </value>
                </member>
                <member>
                    <name>faultString</name>
                    <value>[NoFieldFound]No field found: Lead._FinalOpportunityAmount</value>
                </member>
            </struct>
        </value>
    </fault>
</methodResponse>

potentially relevant:
https://community.infusionsoft.com/t/intermittent-no-field-found-errors-for-existing-fields/36972