Blog post titles are not underlined

Although I have tried adding all kind of css, post titles are not underlined on Blog page.

When I add .entry-title {text-decoration: underline;} it displays underlined titles in Customizer, but not on the page although I delete all the cache multiple times.

I also tried
.entry-title a,
.entry-title a:visited,
.entry-title a: hover {
text-decoration: underline !important;
}

but again nothing happens.

Thank you