Hola,
Here is the code I promised you, like I said the messenger was converting it to a button.
The green highlighted section is the CSS code that make the link into a button. The Yellow highlight is for you to remember to add your site URL.
<a class-"btn btn-primary" rel="noreferrer" target="_blank" href="change this to your site url/Anim_Flash/ISO/ISO_2015_Inf.swf">Información del Curso</a>
Example:
This is what the button looks like. However, the Elegance theme styles this flat and will look good on your site if you choose to use it.
Like I said I think the problem is your Text Editor. The fact that Essentila is built differenlty may also be the reason it wokrs better in that theme.
The Default Text Editor in Moodle is called ATTO. This is porbbably what you are using. We know this can be a problem in themes as it strips all your code, so for this reason many of us tend to use TinyMCE which is smarter and has more options.
Hope this helps?
Mary