Thread:Extension talk:OpenID Connect/Problem authenticating to Google/reply

Sorry, I just saw this. It should not be trying to authenticate with Google on each page. Once it has successfully authenticated, it does not need to contact Google again. So, it sounds like it is not authenticating correctly on that first page. Does it change the links at the top to indicate you are successfully logged in? You could turn on MediaWiki debug logging and check the log file for messages from the extension.