RDFa markup not picked up in extractors


I'm working on a project for the Dutch Kadaster and we're trying to improve findability of the datasets by adding Schema.org markup to the pages (as RDFa).
For example:


The RDFa is valid, yet the data is not detected by, for example, the Google Structured Data Testing Tool:


If I put the same HTML on a different server, it works fine:


So there is something about how the file is served from data.pdok.nl host that prevents extraction, but I can't for the life of me figure out what.

Is someone able to give me a pointer?


John Walker
Principal Consultant & co-founder
Semaku B.V.
SFJ 4.009, Torenallee 20, 5617 BC Eindhoven
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Email: john.walker@semaku.com
Skype: jaw111
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Received on Friday, 9 December 2016 10:24:03 UTC