Oauth Generate Access Token Fails- Regeneration of same token

[meenap3]

Extracting SessionID from Backend and regenerating same in oauth but

Oauth Generate Access Token is failing with

{"ErrorCode" : "invalid_client", "Error" :"Client identifier is required"}. Can you please quick help on this.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<OAuthV2 name="OAuth_GenerateToken">
 <DisplayName>OAuth_GenerateToken</DisplayName>
 <Attributes/>
 <ExternalAccessToken>SessionID</ExternalAccessToken>
 <ExternalAuthorization>true</ExternalAuthorization>
 <Operation>GenerateAccessToken</Operation>
 <GenerateResponse enabled="true"/>
 <StoreToken>true</StoreToken>
 <SupportedGrantTypes>
 <GrantType>client_credentials</GrantType>
 </SupportedGrantTypes>
 <!--GrantType>message.header.grant_type</GrantType>
 <ClientId>message.header.Authorization</ClientId>
 <Authorization>message.header.Authorization</Authorization-->
 <Tokens/>
</OAuthV2>

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<AssignMessage async="false" continueOnError="false" enabled="true" name="Assign_ExternalAccessTokenStatus">
<DisplayName>Assign_ExternalAccessTokenStatus</DisplayName>
<Properties/>
<!--Set>
<Headers>
<Header name="grant_type">client_credentials</Header>
<Header name="client_id">xxxx</Header>
<Header name="Authorization">Basic xxxx</Header>
</Headers>
</Set-->
<AssignVariable>
<Name>oauth_external_authorization_status</Name>
<Value>true</Value>
</AssignVariable>
<IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
<!--AssignTo createNew="false" transport="http" type="response"/-->
</AssignMessage>