Headings after an H4 tag are not displayed

I have a blog post that starts with an H4 heading tag. My problem is the succeeding heading tags(H1 to H3) are not displayed in the table of contents.

Is there a way to show H1,H2,H3 heading tags even if the blog post starts with a lower level heading tag such as H4?

Sample heading structure:
<h4>H4 Heading</h4>
<h2>H2 Heading 1</h2>
<h3>H3 Heading 1.1</h3>
<h3>H3 Heading 1.2</h3>
<h2>H2 Heading 2</h2>
<h3>H3 Heading 2.1</h3>
<h3>H3 Heading 2.2</h3>
<h2>H2 Heading 3</h2>