The AMP plugin for WordPress makes it incredibly easy to support AMP pages on your blog. However, there’s a common structured data validation error for AMP that many blogs experience. That error is “A value for the logo field is required.”
This can be fixed by adding a Site Icon in the Site Identity settings of your theme. To access it, go to Appearance > Customize.
Then click on Site Identity and upload a new Site Icon.
After you do that, go validate your AMP page using Google’s Structured Data Testing Tool and that error should be gone.