I tried submitting the build to app store connect and it got rejected because the watch ads button didn't do anything. Here's the message they sent me:
Test ads and real ads work in the Xcode simulator but they don't work when I try them on my iPad. Any help is appreciated.
ADMOBS disable ad serving if you have not yet verified your billing adress, you do this by entering a pin code they send you via mail.
That can be one reason, will say if you log in to your admobs dashboard.
Otherwise, your app has to be published on app store for admobs to show ads, else it will just be TEST ADS.
So if your test ads are not showing, like fredrik said you have probably not done the events correctly, load the ad, then show it.