I have seen a weird problem on my samsung Galaxy S8, the ads were working perfect till yesterday, only i receive a new patch of update for Android P. i did that update and now the Ads are just flashing on my device and then get removed automatically in fraction of second, on all other devices it works perfect.
I tried contact FB for Audience Network support, they said i need to use the latest SDK i.e 5.3.1 may be. I am not sure what Version Corona is using in its plugin but it must be old one as i saw its not updated since April 2018.
Also is there any complaint of this behaviour of Ads, for your knowledge i will explain once again. When i call Ads.show, It loads the Ads and immediately remove the Ad in just 1 second and this happens only after the latest update on my Samsung S8 plus last night, All the games that i have built using the Corona is doing same behaviour. The Ads are loading good and staying good on other devices though.
Please look into the matter before it gets big as this is causing problem now for Ad click conversion rate now, this is for Admob and FB both.