My changes do not appear online, what can I do?
If your styles are not applied after saving them, it might be due to a caching issue. When your styles are not applied online, make sure that you clear your WP cache (your WP plugin if you have one), your server cache (if you have one. In this case, you can contact your hosting provider), and your browser cache after that you save changes: https://codex.wordpress.org/I_Make_Changes_and_Nothing_Happens
This problem can also be due to a theme-related issue. For instance, the CSS of a theme which overrides the one of Elementor. To be sure that it is a theme issue, switch to a default theme of WordPress such as Twenty Sixteen and if it solves the problem, contact the developers of your theme.
If you use another page builder, it can override the content built with Elementor and you will see online the content written via the conflicting page builder and not the one written with Elementor. To fix this issue, save the page as a template and used the template on a new page. Check the following article to see how it is possible to save pages as templates: https://docs.elementor.com/article/60-library