How to resolve Invalid_grant error in OAuth2

[ankitt...@gmail.com]

I try to authorize the Adwords account but I got the error "invalid_grant". 

https://developers.google.com/adwords/api/docs/guides/authentication

https://developers.google.com/oauthplayground/#step1&scopes=https%3A//www.googleapis.com/auth/adwords&url=https%3A//&content_type=application/json&http_method=GET&useDefaultOauthCred=checked&oauthEndpointSelect=Google&oauthAuthEndpointValue=https%3A//accounts.google.com/o/oauth2/v2/auth&oauthTokenEndpointValue=https%3A//oauth2.googleapis.com/token&includeCredentials=unchecked&accessTokenType=bearer&autoRefreshToken=unchecked&accessType=offline&forceAprovalPrompt=checked&response_type=code

I try to generate refresh token on above URL. but I am getting 302 Found Error. Please help me