Login session not found

I am trying to get task list matching the pattern.I am using the following request payload:
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:int="http://corrigo.com/integration/" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<soap:Header>
<int:CorrigoNetOptions>
<int:ImposeConcurrencyId>false</int:ImposeConcurrencyId>
<int:UpdateLastModified>false</int:UpdateLastModified>
<int:CanDeleteMissingEntity>false</int:CanDeleteMissingEntity>
<int:LockOnDataRetrieval>Default</int:LockOnDataRetrieval>
</int:CorrigoNetOptions>
</soap:Header>
<soap:Body>
<int:RetrieveMultiple>
<int:queryExpression xsi:type="int:QueryExpression" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<int:EntityType>Task</int:EntityType>
<int:PropertySet xsi:type="int:PropertySet">
<int:Properties>
<int:string></int:string>
<int:string>Specialty.</int:string>
</int:Properties>
</int:PropertySet>
<int:Orders>
<int:OrderExpression>
<int:PropertyName>Id</int:PropertyName>
<int:OrderType>Ascending</int:OrderType>
</int:OrderExpression>
</int:Orders>
<int:Count>10</int:Count>
<int:FirstResultIndex>0</int:FirstResultIndex>
<int:Criteria>
<int:Conditions>
<int:ConditionExpression>
<int:PropertyName>DisplayAs</int:PropertyName>
<int:Operator>Like</int:Operator>
<int:Values>
<int:anyType xsi:type="xsd:string">%cafe%</int:anyType>
</int:Values>
</int:ConditionExpression>
</int:Conditions>
<int:FilterOperator>And</int:FilterOperator>
<int:Filters>
<int:FilterExpression>
<int:Conditions>
<int:ConditionExpression>
<int:PropertyName>IsRemoved</int:PropertyName>
<int:Operator>Equal</int:Operator>
<int:Values>
<int:anyType xsi:type="xsd:boolean">false</int:anyType>
</int:Values>
</int:ConditionExpression>
</int:Conditions>
</int:FilterExpression>
</int:Filters>
</int:Criteria>
<int:Distinct>true</int:Distinct>
</int:queryExpression>
</int:RetrieveMultiple>
</soap:Body>
</soap:Envelope>

And also using SOAPACTION at login.