Always getting Access token expired error generating the Access and Refresh Token from Grant Token

Always getting Access token expired error generating the Access and Refresh Token from Grant Token

I'm working to migrate our API integration in C# from v1 to v2. I've added my Client Id but always I get the same error executing the GenerateAccessToken method to generate the access token 'Access token expired'. I've set the time to expiry in 10 min. Any idea what should be other reason to fail?

I'm using aaaserver.profile.READ,ZohoCRM.users.ALL,ZohoCRM.modules.ALL,ZohoCRM.settings.ALL in scopes.