I have created new space from template. Now when I modify dashboard and save it I got an error "Unable to communicate with server. Saving is not possible at the moment.".
If I close it and try to edit again I get message "A version of this page you were editing at 2 minutes ago was saved as a draft. Do you want to view the change, resume editing or discard it?" If I select discard I get "An unknown error has occurred. Please check your logs."
I stopped server, removed all drafts in DB as described here "https://confluence.atlassian.com/confkb/removing-orphaned-draft-316113059.html", started the server. All looks good, but if try to edit dashboard I got the same errors.
I can add new pages but cannot edit them after initial save. I have checked log files in /opt/atlassian/confluence/logs/ and /var/atlassian/application-data/confluence/logs and none of them contains any errors. My configuration includes AWS Linux, Confluence 6.12 (b 7901) installed from installer. Nginx as https proxy, all proxy settings are done according to confluence doc and there are no warning about hose as well.
What else can check to understand the reason for this?