Wordpress cant edit pages (offline)

Seeing how you’re using both WordPress and Cloudflare, please note that Cloudflare uses “Flexible SSL” by default, and WordPress doesn’t work well with that out of the box. The “Automatic HTTPS Rewrites” is a Cloudflare setting that people tend to use to try and work around, but that option tends to cause inexplicable errors like this.

So you need to disable Automatic HTTPS Rewrites and configure your website properly.

There are two ways to solve that: