This structured data markup error is a very frequently asked question in various forums.
When you check your blog post with Google Structured Data Testing Tool, it shows this remark:
"Missing: Author"
This is another very easy structured data markup problem to overcome.
How To Fix Missing Author In Blogger Template
Just follow closely the tutorial below now.
This is what you do:
1. Sign into your Blogger account.
2. Click "Theme".
3. Then click "Edit HTML".
4. Look for the following code in your template
<span class='post-author vcard'>
<b:if cond='data:top.showAuthor'>
<b:if cond='data:post.authorProfileUrl'>
<span class='fn'>
<a expr:href='data:post.authorProfileUrl' rel='author'
title='author profile'>
<data:post.author/>
</a>
</span>
<b:else/>
<span class='fn'><data:post.author/></span>
</b:if>
</b:if>
</span>
5. Replace it with the following code:<b:if cond='data:top.showAuthor'>
<b:if cond='data:post.authorProfileUrl'>
<span class='fn'>
<a expr:href='data:post.authorProfileUrl' rel='author'
title='author profile'>
<data:post.author/>
</a>
</span>
<b:else/>
<span class='fn'><data:post.author/></span>
</b:if>
</b:if>
</span>
<span class='post-author vcard' itemscope='itemscope'
itemtype='http://schema.org/Person'>
<b:if cond='data:top.showAuthor'>
<b:if cond='data:post.authorProfileUrl'>
<span class='fn author'>
<a expr:href='data:post.authorProfileUrl' rel='author'
title='author profile'>
<span itemprop='name'><data:post.author/></span>
</a>
</span>
<b:else/>
<span class='fn author'><span
itemprop='name'><data:post.author/></span></span>
</b:if>
</b:if>
</span>
6. Click the "Save theme" button.itemtype='http://schema.org/Person'>
<b:if cond='data:top.showAuthor'>
<b:if cond='data:post.authorProfileUrl'>
<span class='fn author'>
<a expr:href='data:post.authorProfileUrl' rel='author'
title='author profile'>
<span itemprop='name'><data:post.author/></span>
</a>
</span>
<b:else/>
<span class='fn author'><span
itemprop='name'><data:post.author/></span></span>
</b:if>
</b:if>
</span>
7. That's all.
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