After implementing native ads by following this codelab every thing worked, then I integrated it into my app, it shows the test ads perfectly, but when I want to deploy I head to https://apps.admob.com to create my ads unit and app id to replace the test one from Codelab.
From the admob page there is no option for native ad unit, I only saw.
I created banner ad unit hoping it will work, since I could not find native ad unit precisely. But after every trial no ads showed up.
Native Advanced Ads is currently a limited beta release. If you're interested to participate in the Native Advanced beta release, you will have to reach out to your Technical account manager. If you do not have a technical account manager, you can contact the AdMob Product Support team and they will be able to assign you one. You can reach out to the AdMob Product Team through the Contact Us button on the upper right corner of this page.