I'm getting a "Not found, error 404" message when editing a page. This started happening after upgrading to the latest version of WordPress
The pages are there and they display fine on the site but the issues appears in the admin panel when trying to edit.
- I've tested out reverting to a backup before the upgrade and it works fine, no issue.
- Disabled all plugins and the issue still remains.
- Changed to the default 2015 theme and the issue still remains.
- Went to the permalinks page and clicked save but the issue still remains.
What are some suggestions of what to try next?