I would reboot.

Theoretically the problem is solved: https://proconnect.intuit.com/community/lacerte-news-and-updates/discussion/error-502-bad-gateway-wh... (added by moderator: Article was Removed, as its no longer an issue) 

Reboot tried, but did not resolve the issue.  Thank you for the link to the Lacerte's explanation.  Hopefully will be resolved soon.

I believe that it is sometimes an Anti Virus issue. Try temporarily disabling your AV software.