Be aware of these changes in your browser.
Today Chrome blocks requests on HTTPS pages for services that are HTTP. This started in the first half of this year. Not all Chromium-based browsers have this security measure. To workaround this, you have to run both Ratel and the cluster with TLS enabled. Or use another browser that doesn’t have this limitation. This also affects the Tour.
You can also run a Ratel image locally with no HTTP to connect your your NON-HTTPS Dgraph cluster.
By the way, Chrome will implement in its 92 version(will be released July this year), in a mandatory manner, the end of sending requests by static or dynamic pages in the browser to services on the local network. This means that requests made by Ratel to a local Dgraph cluster can be blocked. Maybe there will be a way to allow this request. But it will certainly not be a trivial action to do.
These are anti Cross-site request(CSRF or XSRF) security measures. A measure against attacks on router admin pages for example and so on.
BTW, always change your Router’s password!