When building and editing websites on the Duda platform, it is secured by a secure connection. You can tell this by looking at your browser bar and seeing a secure lock symbol. Each browser is a bit different, here's what it looks like in Chrome:
This makes sure that communication between you and the Duda service is secure and no one is in the middle listening. This has quite a few benefits, but also brings some issues.
Below you will find a few paths to troubleshoot this issue.
Force the content load over HTTPS
The first and best steps should be to try and load the custom code over an HTTPS connection. To do this, you will need to edit the code slightly and find the reference to http://. You can try adding an s to the http:// so that it becomes https://. This will force the content to load over a secure connection and thus work inside of the secure browser connection.
Switch off the secure connection to Duda
One simple option is to turn of the secure connection to Duda, inside of your address bar. What you will want to do is start editing the URL and remove thes from the https:// and hit return. This will force Duda to load the editor over a non-secure connection and allow you to embed your content.