Hello.
I have also same problem in UE 4.22.
arm7 works, but arm64 is not working.
I moved all plugins to project’s plugins folder, then a message of UniversalMobileAds like former post disappeared.
but Interstitial Ad is not showing.
I tried let gameDNAinstaller re-install again for UniversalMobileAds.
And removed test device id, however still not working.
pls