“When you first install WordPress Popular Posts and after every plugin update, flushing your site’s page cache is highly recommended to make sure that WPP can insert its JavaScript code into your posts and pages correctly.”
After flushing my site’s page cache the plugin seems work, i’ll update you in 4-5 days if this is the definitivile solution, thanks!
Anyway, I don’t want to change the font size just to have post title like h5. I need to improve SEO on-site changing headings of the page. So I’d like to know how to modify precisely h2 in h5, not just a lookalike.