Get OAuth V2 Info policy not working

[#1]

<PreFlow name="PreFlow">
        <Request>
            <Step>
                <Name>OAuth-v20-1</Name>
            </Step>
            <Step>
                <Name>Get-OAuth-v20-Info-1</Name>
            </Step>
        </Request>
        <Response/>
    </PreFlow>

OAuthV2:

<OAuthV2 async="false" continueOnError="false" enabled="true" name="OAuth-v20-1">
    <DisplayName>OAuth v2.0-1</DisplayName>
    <Properties/>
    <Attributes/>
    <ExternalAuthorization>false</ExternalAuthorization>
    <Operation>VerifyAccessToken</Operation>
    <SupportedGrantTypes/>
    <GenerateResponse enabled="true"/>
    <AccessTokenPrefix/>
</OAuthV2>

GetOAuthV2Info:

<GetOAuthV2Info async="false" continueOnError="false" enabled="true" name="Get-OAuth-v20-Info-1">
    <DisplayName>Get OAuth v2.0 Info-1</DisplayName>
    <AccessToken ref="request.queryparam.access_token"/>
</GetOAuthV2Info>

I am trying to retrieve the attributes for a access_token using the GetOAuthV2Info policy. But response returning the error 401 unauthorized.

Why am I getting this error?