Unity AdMob - Ads showing only on some devices

I just added AdMob to my Unity Game but there are some devices that it doesn’t show up any ads and some devices that display only some ads.

On the Samsung Galaxy S7, Cubot X15 and Google Nexus 5 all ads are displayed. On a Huawei Honor banners are not displayed (only interstitials and rewardedAds).

Any ideas?

Thanks in advance.

I had the same problem and I fixed it by connecting the device to the internet. Admob requires internet connection to work. Maybe your device is not connected?