Try:
<GetOAuthV2Info name="GetTokenAttributes">
<AccessToken ref="request.queryparam.access_token"></AccessToken>
</GetOAuthV2Info>
or
<GetOAuthV2Info name="GetTokenAttributes">
<AccessToken>{request.queryparam.access_token}</AccessToken>
</GetOAuthV2Info>
Your original policy is probably using the literal string value of request.queryParam.access_token
as the token reference. Also noticed that queryparam
is complete lower case.