invalid_grant trying to get oAuth token from google
I keep getting an invalid_grant error on trying to get an oAuth token from Google to connect to their contacts api. All the information is correct and I have tripple checked this so kind of stumped.
Does anyone know what may be causing this issue? I have tried setting up a different client id for it but I get the same result, I have tried connecting many different ways including trying the force authentication, but still the same result.
Answer
I ran into this same problem despite specifying the "offline" access_type in my request as per bonkydog's answer. Long story short I found that the solution described here worked for me:
https://groups.google.com/forum/#!topic/google-analytics-data-export-api/4uNaJtquxCs
In essence, when you add an OAuth2 Client in your Google API's console Google will give you a "Client ID" and an "Email address" (assuming you select "webapp" as your client type). And despite Google's misleading naming conventions, they expect you to send the "Email address" as the value of the client_id parameter when you access their OAuth2 API's.
This applies when calling both of these URL's:
Note that the call to the first URL will succeed if you call it with your "Client ID" instead of your "Email address". However using the code returned from that request will not work when attempting to get a bearer token from the second URL. Instead you will get an 'Error 400' and an "invalid_grant" message.