Please make sure that you're making the changes in the correct theme file pointed at by SCLogin > Login View Settings > Theme option. It can be easy to put the changes in the wrong one especially if you've made your own theme. After you've made the CSS changes, please make sure to clear your cache before reloading the page on the front-end.
If this still does not help, please send me a URL to your site. I should be able to inspect it to see the CSS file.