I recently upgraded to 2.1.1 and am now trying to enable Google API single sign on. I followed the directions  and can get to the 'Login with Google' button, but when I click it, I am redirected to Google and then shown this error:

Error: invalid_client

no application name
Request Details

cookie_policy_enforce=false
https://www.googleapis.com/auth/userinfo.email 
response_type=code
access_type=online
redirect_uri=http://forum.galleryserverpro.com/auth.aspx?auth=google
display=page
client_id=XXXXXXXX

I don't know what is causing this but one thing I wonder is whether I have the right API enabled in Google. Their APIs page list dozens of APIs you can enable. Which one is required for SSO? I've tried Contacts API and Google+ API.

Edit: You can see for yourself at http://forum.galleryserverpro.com 

Thanks,
Roger Martin
Lead Developer and Creator, Gallery Server Pro
http://www.galleryserverpro.com 

Looks like one field is empty.

try the solution posted on Stackoverflow 

http://forum.galleryserverpro.com 

Thanks!
Roger

http://forum.galleryserverpro.com 

Thanks!
Roger

Which option do you choose

Login with a user account that is connected with Google. Or if no account is found a new account will be automatically created in the forums.

or

Login with a user account that is connected with Google. Or if no account is found a new account will be automatically created in the forums.
Connect an existing forums account with your Facebook account You need to login thru the forums first. The Google email address must match the forum user email address to connect the user.

The first option. I'm trying to test the scenario where a first-time user comes to my forum and uses their Google account to log in.

The first option. I'm trying to test the scenario where a first-time user comes to my forum and uses their Google account to log in.

In that case the error message comes only when the email address of the google user already exists as user in the forum. I change the error message to make this better understandable.

Ahh, OK. I tried using a Google account whose email wasn't used by any forum accounts and was able to authenticate, so it appears you are right.

Thanks for you help. Great product!

Roger