Have you tried doing this without the iframe? When sprite button is clicked, do "Browser - Go to URL" or "Browser Open URL in new window". Put the same URL you have in that hyperlink.
Another option you can try is sending a "fake" click to the hyperlink. Add an ID "myHyperlink" to the hyperlink. Move the iframe off-screen, so it's not visible. On sprite button clicked, add an action "Browser Execute javascript" with code "myHyperlink.click()"