@scheky’s solution worked perfectly for me.
Make sure you use a text editor that shows line numbers, so you can find Row 265 in nextend-google-connect.php.
This is a big file, and there is more than one line with the following function call:
function new_google_login_action()
So be careful you’re only changing the one on line 265.
Several people have mentioned deleted and adding the “Google Application”. I needed to do this also before the fix worked.
More precisely, I deleted and re-created my “Client ID for web applications”, which is in the API Access tab at https://code.google.com/apis/console
Thanks to @scheky!!!