As I mentioned before, most newer themes have the entity-title code in them. The other easiest way to fix this error is to use a newer theme. If you're firmly tied to your older theme, here is the code you need to have in place to clear the Google error.

<span class="entity-title">your WordPress theme's title coding</span>

You will have to determine which file or files control the title text of your WordPress posts and pages. Usually it will be blocked by <h1> or <h2> (if it is the blog / tag / category loop). Usually the file is content.php, or loop-blog.php, or loop-single.php - but it could appear in any number of files. You can add the class="entity-title" directly to the h1 or h2 block or use the span code.

There may be multiple places within the file where you need to make this fix, depending on how complex or flexible your theme is.

Once you feel like you have made all the code additions necessary, save the file. WordPress will acknowledge the file saved successfully.

View your site with your browser to be sure it still loads. If it does, great. If not, upload the copy of the original file you copied to your local machine back to your hosting site, and try again... or quit and hire someone else to do it.

Note which files have the title coding. These same files will need the author fix and date updated fix.