Page Header not showing up on Posts page

Hi,
I created a custom page header, then assigned it to all Global Locations.

The Page Header includes the following code:
<h1 class="header1">{{post_title}}</h1>

It works on all pages except the page that shows my latest posts, which is /blog/.

On the Blog page, it renders <h1 class="header1"></h1>, but it doesn't include the page name, Blog.

The same thing happens on the Search results page.

Again, I have the custom page header assigned to all of the Global Locations, so I'm not sure what the problem is. Please advise. Thanks in advance.