I am having an issue setting up OAuth credentials for Google. My n8n instance is running on 192.x.x.x:5678 and not localhost. I am having difficulty figuring out how to set up api access to Google services. In Google console, if I enter the URI as localhost, it does not work on my end. And Google will not allow my specific host of 192.x.x.x as it requires .com, .org, etc for anything other than localhost.
Then I added port mapping for 5678:5678. Restarted the nginx container, and was able to connect. Just a little added information, my nginx container is running on a different machine then my n8n container. So, you may need to change some things a little to suit your circumstances.