I am using OpenGraph tags so when I share my page on Facebook or Google+, those services will know what image should be displayed in the share dialog.
<meta property="og:title" content="Best Site Ever" />
<meta property="og:description" content="This website rules" />
<meta property="og:image" content="http://example.com/image.png" />
Both services were displaying the correct image, but I changed the image (and filename) in og:image. Only Facebook is showing the new image, after running it through their URL debugger. Google+ is showing the old image, I also ran my URL through their debugger, but the image will not update. Anyone know why?
Best How To :
Use the structured data tool to check what metadata / schema Google is parsing out. Also, sometimes the service is caching data, try appending an anchor or parameter to your URL while testing (e.g. https://foo.com becomes https://foo.com/#test1 https://foo.com?bar=1). The time it takes for the cache to invalidate is not known, so the only consistent way to force the crawler to recalculate the snippet that appears for your page is to change the url.
You might want to try generating schema using the Google+ snippet tool. Also, note that article rendering has requirements that you can follow to control how images appear in the stream. Note that if you want your content to render with a large image, you must specify article, blog, or blog posting for the schema type.