The most common cause of this is a problem reaching the Synchrony service.
Check this by going to Admin -> Collaborative editing, and disabling it. You should find that you can now edit pages, but with the old Confluence 5 style editor. If that happens, then we'll need to look at Synchrony.
My instinct would be to look at the proxy server.
I had massive problems getting Synchonry to work over https behind an Apache proxy on 6.0. On 6.2+ it works fine if you follow all the docs, but you still do have to fiddle with the proxy setup for it quite a bit.
More and more people are building their careers with Atlassian, and we want you to be at the front of this wave! Important Dates Start the Certification Prep Course by 2 April 2019 Take your e...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs