Schema Markup Showing On Some Pages But Not Others

[GManSEO]

We have implemented Schema markup for Reviews on product pages.  All these pages check out in the Markup Checker Tool in Webmaster Tools, but out in the wild only about 50% of them are actually showing the Review markup in SERPs.

Example of a page showing Review markup successfully:

http://www.cloud9living.com/los-angeles/drive-a-stock-car

And example of a page not showing markup in the SERPs:

http://www.cloud9living.com/las-vegas/race-a-ferrari

Any ideas on why some SERPs show markup and others do not?

Thanks!

[TLAVA]

I have had the same issues and am still working on them but this tool http://linter.structured-data.org/ has help find markup that google validates but has Word copy and paste chars in it that cause errors.

[MatthewBarby]

Rich snippets can be fairly tempermental. They don't always show up in the search results and Google have came out and said this (https://support.google.com/webmasters/answer/1093493?hl=en).

I have some snippets that show on my travel blog that have been there for months and then just vanish - it's pretty annoying, but one thing I would check is that they follow Google's Webmaster guidelines (you can see them in the link above).

Hope this helps.

Matt