使用WSO2 Micro Integrator对接Dynamics 365创建实体时自动令牌生成遇401错误

我在使用WSO2 Micro Integrator结合Dynamics Connector操作CRM Dynamics 365（v9.2实例）创建实体时，手动配置<accessToken>******</accessToken>功能正常，但因为令牌存在有效期，我尝试了如下自动生成令牌的配置，却出现401未授权错误：

<resource methods="POST" uri-template="/create">
  <inSequence>
    <log />
    <property
      name="client_id"
      scope="default"
      type="STRING"
      value="***********"
    />
    <property
      name="client_secret"
      scope="default"
      type="STRING"
      value="***********"
    />
    <property
      name="grant_type"
      scope="default"
      type="STRING"
      value="client_credentials"
    />
    <property
      name="resource"
      scope="default"
      type="STRING"
      value="https://***********.com"
    />
    <payloadFactory media-type="xml">
      <format>
        <soapenv:Envelope
          xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
        >
          <soapenv:Body>
            <root>
              <client_id>$1</client_id>
              <client_secret>$2</client_secret>
              <grant_type>$3</grant_type>
              <resource>$4</resource>
            </root>
          </soapenv:Body>
        </soapenv:Envelope>
      </format>
      <args>
        <arg evaluator="xml" expression="$ctx:client_id" />
        <arg evaluator="xml" expression="$ctx:client_secret" />
        <arg evaluator="xml" expression="$ctx:grant_type" />
        <arg evaluator="xml" expression="$ctx:resource" />
      </args>
    </payloadFactory>
    <property
      name="messageType"
      scope="axis2"
      type="STRING"
      value="application/x-www-form-urlencoded"
    />
    <property
      name="DISABLE_CHUNKING"
      scope="axis2"
      type="STRING"
      value="true"
    />
    <call>
      <endpoint>
        <http
          method="post"
          uri-template="https://login.microsoftonline.com/304d868c-e271-4a91-8965-f24dedd79ccf/oauth2/token"
        >
          <suspendOnFailure>
            <initialDuration>-1</initialDuration>
            <progressionFactor>-1</progressionFactor>
            <maximumDuration>0</maximumDuration>
          </suspendOnFailure>
          <markForSuspension>
            <retriesBeforeSuspension>0</retriesBeforeSuspension>
          </markForSuspension>
        </http>
      </endpoint>
    </call>
    <propertyGroup>
      <property
        expression="json-eval($.access_token)"
        name="token"
        scope="default"
        type="STRING"
      />
    </propertyGroup>
    <log>
      <property expression="get-property('token')" name="tt" />
    </log>
    <msdynamics365.init>
      <accessToken>{get-property('token')}</accessToken>
      <apiUrl>https://***********.com</apiUrl>
      <apiVersion>v9.2</apiVersion>
      <refreshToken>0.AR8ATWbW27lO60aZ2FxDuhU8Yas</refreshToken>
      <clientSecret>***********</clientSecret>
      <clientId>***********</clientId>
      <resource>https://***********.com/</resource>
    </msdynamics365.init>
    <msdynamics365.createEntity>
      <entityType>ext_APICreateOffre</entityType>
      <bodyContent>{json-eval($)}</bodyContent>
      <queryParam
        >name,refOffre,typeOffre,commitment,promotionBeginDate,promotionEndDate,promotionalOffer,products</queryParam
      >
    </msdynamics365.createEntity>
    <respond />
  </inSequence>
  <outSequence />
  <faultSequence />
</resource>

更新：

内容的提问来源于stack exchange，提问作者Oussama Nairi