Unity Banner Ad not work in some apps.

How to setup Banners ?

I have one app using Monetize 3.0 ads for Android the banner works fine no issue at all.
I go to the Dashboard operate create a new Banner placement set my ID in the game and works fine.

Then I try the same for a new app I can load rewarded video ads, but when I try to load the new banner ads it always return
"Could not show banner due to No fill for placement 'banerID'"
I'm loading the banners in test mode, after you create the Placement for the banner should we have to make another step in the operate dashboard?

I'm loading the correct App id and Placement ID but the test mode is not working.
Anyone had a similar issue like these ?
One app works fine in test environment but in another one it doesn't work.