Full Error Message:
Google 502. That’s an error. The server encountered a temporary error and could not complete your request. Please try again in 30 seconds.

Screenshot of error coming from Google Server (will have Google logo at top):

If you see an error message that is coming from Google, their server may be temporarily down and you need to wait a little while to see if error/server resolves itself. If you want to check if there are Google server outages, use this link:  https://www.google.com/appsstatus#hl=en&v=status. You will see an orange dot visible if there is a server outage which you can click on for more detail.