AdMob bannerView not showing after following the docs - ios

Question

I'm trying to show ads in my app, and I have chosen AdMob. I have done everything as they wrote in the docs.
I added this to the AppDelegate:
GADMobileAds.sharedInstance().start(completionHandler: nil)
I also added this code to the viewDidLoad:
override func viewDidLoad() {
super.viewDidLoad()
setUpView()
adBannerView.adUnitID = "ca-app-pub-3940256099942544/2934735716"
adBannerView.rootViewController = self
adBannerView.load(GADRequest())
}
The adBannerView is a UIView in main.storyboard that has GADBannerView as subclass (also, it's connected via #IBOutlet.)
But, the ad isn't showing in the simulator. I get this error message every so often (prob when it refreshes)
2020-10-05 19:36:47.683540+0200 Learn Chemistry[38879:1067024] WF: _userSettingsForUser : (null)
2020-10-05 19:36:47.683687+0200 Learn Chemistry[38879:1067024] WF: _WebFilterIsActive returning: NO
2020-10-05 19:36:50.123788+0200 Learn Chemistry[38879:1067024] [Process] 0x7fd3fe019420 - [pageProxyID=31, webPageID=32, PID=39055] WebPageProxy::didFailProvisionalLoadForFrame: frameID = 3, domain = NSURLErrorDomain, code = -1200
2020-10-05 19:36:50.164032+0200 Learn Chemistry[38879:1067024] [assertion] Error acquiring assertion: <Error Domain=RBSAssertionErrorDomain Code=3 "Target is not running or required target entitlement is missing" UserInfo={RBSAssertionAttribute=<RBSDomainAttribute| domain:"com.apple.webkit" name:"Background" sourceEnvironment:"(null)">, NSLocalizedFailureReason=Target is not running or required target entitlement is missing}>
2020-10-05 19:36:50.164192+0200 Learn Chemistry[38879:1067024] [ProcessSuspension] 0x147efe1c0 - ProcessAssertion: Failed to acquire RBS Background assertion 'WebProcess Background Assertion' for process with PID 39055, error: Error Domain=RBSAssertionErrorDomain Code=3 "Target is not running or required target entitlement is missing" UserInfo={RBSAssertionAttribute=<RBSDomainAttribute| domain:"com.apple.webkit" name:"Background" sourceEnvironment:"(null)">, NSLocalizedFailureReason=Target is not running or required target entitlement is missing}
2020-10-05 19:36:50.174754+0200 Learn Chemistry[38879:1067024] [assertion] Error acquiring assertion: <Error Domain=RBSAssertionErrorDomain Code=2 "Specified target process does not exist" UserInfo={NSLocalizedFailureReason=Specified target process does not exist}>
2020-10-05 19:36:50.174900+0200 Learn Chemistry[38879:1067024] [ProcessSuspension] 0x147efe240 - ProcessAssertion: Failed to acquire RBS Background assertion 'WebProcess Background Assertion' for process with PID 39055, error: Error Domain=RBSAssertionErrorDomain Code=2 "Specified target process does not exist" UserInfo={NSLocalizedFailureReason=Specified target process does not exist}
2020-10-05 19:37:20.127313+0200 Learn Chemistry[38879:1067024] Could not signal service com.apple.WebKit.WebContent: 113: Could not find specified service
Is there anything I did wrong?
thank you.
BSM