I am on Arch Linux and today upgraded GNOME to 3.18. 

Unfortunately anything relying on GOA seems to be messed up now. The Google accounts were shown as expired, however, re-authenticating didn't help, instead I had to re-add the account. Now empathy fails to authenticate with Google talk, Google drive support in Nautilus does nothing (first I get "Operation already pending", and then a timeout alert), also my owncloud share appears in Nautilus but cannot be mounted, for the same reason (I see goa timout messages in Syslog), while mounting it manually via a WebDAV URI works flawlessly. 

This is what I see when I try to get empathy to re-logon with google chat: 
Okt 09 10:49:51 tommy dbus-daemon[3925]: Activating service name='org.freedesktop.Telepathy.Client.Empathy.Auth'
Okt 09 10:49:51 tommy dbus-daemon[3925]: Successfully activated service 'org.freedesktop.Telepathy.Client.Empathy.Auth'
Okt 09 10:51:15 tommy org.gnome.OnlineAccounts[3925]: (goa-daemon:4057): GoaBackend-WARNING **: secret_password_lookup_sync() returned NULL
In Evolution ALL calendars except for readonly ICS subscriptions have disappeared.

To in total, it's a complete mess. 

With other users on the same computer the situation is somewhat better, but varied. I have tried to re-authenticate several times, and according to g-o-a everything is fine, but still it's completely dysfunctional.