Error from Google Structured Data Testing Tool

I'm using Google's Webmaster Console to make sure my site meets Google's search criteria. I'm using the Structured Data Testing tool to review my site to find any errors. I have one error that is with my logo file and i don't know how to fix this. Google's response to parsing my website was this "https://www.divinelydog.com/wp-content/uploads/2017/06/Divinely-Dog-Logo-400.png?3841bc (The property logo is not recognized by Google for an object of type WebSite.)" All i see in Customizing > Site Identity > Logo is the Divinely Dog Logo png file I uploaded. Why does Google not understand this .png file? All my media files are png and none of the others are in error? Is this the wrong file type for a logo? Thanks. Martha