Can't create page in confluence - after 30 seconds times out with error

[Micron21 Support]

When attempting to create a new page, the page loads `[myhostnameandport]/pages/resumedraft.action?draftId=15695877&draftShareId=72d47233-7586-4f13-bd50-3c2d68531097&` but after 30 seconds of loading it times out with the error popup `Something went wrong after loading the editor. Copy your unsaved changes and refresh the page to keep editing`

I can edit existing pages fine, and can create spaces fine.

I tried restarting synchrony and confluence, neither with any result. I have tried logging out and back in, and have tried clearing my cache, and a different browser.

The errors I see in the browser console is:
`SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON databatch.js:3380:472`

The atlassian-confluence log shows no logs when I click "create". The atlassian-synchrony log shows:
```
2019-12-09 12:49:47,662 DEBUG [272:StdOutHandler [/opt/atlassian/confluence/jre/bin/java]] {"synchrony":{"request":{"remote-addr":"[my-server-ip]","uri":"/synchrony/heartbeat","request-method":"get","query-string":"_=1575856187628","x-forwarded-for":"[my-client-ip]"},"response":{"status":200},"ns":"synchrony.middleware.logging","level":"info","message":"synchrony.middleware.logging [info] null"}}
2019-12-09 12:49:48,093 DEBUG [272:StdOutHandler [/opt/atlassian/confluence/jre/bin/java]] {"synchrony":{"request":{"remote-addr":"[my-server-ip]","uri":"/synchrony/v1/data/Synchrony-c9722e5c-3311-3852-9f4b-7f9d15b99e29/confluence-15695886","request-method":"post","query-string":"state-at=@head&state-format=type-tagged&rewrite-request=true&cached=true","x-forwarded-for":"[my-client-ip]"},"response":{"status":404},"ns":"synchrony.middleware.logging","level":"info","message":"synchrony.middleware.logging [info] null"}}
```

So it looks like Synchrony is giving me a 404 error.

I've actually solved this whilst building the question logs; my reverse proxy had been configured to redirect on custom-errors. So, the proxy was detecting the 404 error code, and not parsing that to Synchrony but instead displaying a customerrorpage.

Synchrony relies on receiving the 404 page not found error to be able to generate the new page. Be wary with your proxy configurations!

[Kiran Panduga {Appfire}]

Hi @Micron21 Support , 

You can address the Synchrony process error 404, by validating the symptoms and resolution provided in the below Atlassian KB article.

https://confluence.atlassian.com/confkb/collaborative-editing-cannot-be-enabled-because-the-settings-page-does-not-load-946044810.html

Thanks,

Kiran.