I have entered a working web address yet I get no image in the frame.
Any tips?
It is likely you are receiving an error in your Console. In your browser, if you hit F12, this will load developer tools. Open up dev tools and refresh your page, an error should show up.
It is likely that the domain you are loading the image from is blocked in your domain. What you will want to do is allow this domain to be rendered in an iframe.
Go to -> Site Settings, HTML Field Security. On the following page, it will ask you what domains you wish to allow to be loaded in Iframes.
In the text box under “Allow iframes from this domain”, type in the domain the image/webpage is loading from and click ‘Add’.
Hope this helps.