An SEO asked Google's John Mueller why his rich cards (rich snippets) aren't showing up in search. John responded with three possible reasons over Twitter.
The question was "How do I debug why my Google Rich cards are not appearing when the webmaster console says everything ok and the help article doesn't apply?"
John responded:
(1) Technically incorrect (use SDTT)
(2) Not compliant with policies (eg, wrong markup type)
(3) Or general quality issue with site
Got it? He fit it all into a tweet:
3 possible reasons: technically incorrect (use SDTT), not compliant w/ policies (eg, wrong markup type), or general quality issue with site
— John ☆.o(≧▽≦)o.☆ (@JohnMu) August 11, 2017
Forum discussion at Twitter.
