Native Ads are still not fully available

Note: Native Ads Advanced is currently in a limited release. If you're interested in participating, reach out to your account manager to discuss the possibility.

Source: https://developers.google.com/admob/android/native-advanced

To participate you have to contact AdMob. If you can't see any contact button you may earn less than 25$ per week. For more informations visit:

https://groups.google.com/forum/#!topic/google-admob-ads-sdk/f0Ngf-qvYmk

EDIT 2018-02-28:

Today I contacted Admob's email support for native ads. They answered quickly that native ads are only available for a very small group of Admob developers and only with a previous invitiation from Google. There is also still no ETA when it gets released.

EDIT 2018-07-23:

Today Admob suddenly activated native ads for an account I manage. It earns more than 10k a month.

EDIT 2019-08-05:

Today native ads have come out of beta and are now available for all developers

Source: https://www.blog.google/products/admob/native-ads-available-to-all/

The native express ad format has been discontinued

14 March 2018: The native express ad format has been discontinued

According to this :

All native express ad units have now stopped serving ads and have been removed from AdMob. Historical reporting data for these ad units will remain available.