cant Re-Authenticate user using stored authentication detail gdata-objectivec-client
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i am using gdata-objectivec-client for fetching document list from google services,

i am storing the authorization token in keychain store, but next time when i fetch the same authentication detail, i only get refresh_token string, and getting access_token nil..


what to do the authentication detail show i can authenticate [auth canAuthorize] returns true

but when i request using that auth , it show


    <HEAD>
    <TITLE>Authorization required</TITLE>
    </HEAD>


please help me out of this, thanks in advance...