Hi @Lis,
I don’t understand @TINO’s response, so perhaps he’s already said this, but you’re trying to load http content over https. Web browsers don’t like this.
If you open the Developer Tools in your browser, and take a look at the Console, you’ll see a bunch of messages that look something like this:
What this means is you need to look for every instance of http:// in your project (including in your Web Address in General Settings, and any global code areas) and replace them with https://. This won’t have any impact when loading the non-secure version of your site, but will allow everything to work when the secure version of your site is loaded.
You can use the Project Search feature in the new RapidWeaver 7.3 beta to find every http:// link. 
Cheers,
Simon