Sitename won't show up on SEO's title

Hi
I’m experiencing the same issue as this user. And I can’t seem to solve it.

Settings: no forced rewriting.
Title settings, see snapshot: https://cl.ly/image/1L06451m2F1r
Header.php, see snapshot: https://cl.ly/image/3W3n0t120V2T

And yet, as you can see here, for instance, https://megustatupelo.es/cambios-en-el-cabello-en-embarazadas/ the sitename won’t show.

What am i doing wrong? or is it a bug?

Thanks!

https://www.ads-software.com/extend/plugins/wordpress-seo/