I can confirm that Appnext is NOT working with Corona on Android.
I just created a new App in the Appnext panel, used their example App (https://www.appnext.com/plugins/coronaTestApp.zip) and pasted my ad ids there.
This is the complete log:
01-26 20:57:45.754 21162 21175 V Corona : \> Class.forName: network.LuaLoader 01-26 20:57:45.754 21162 21175 V Corona : \< Class.forName: network.LuaLoader 01-26 20:57:45.754 21162 21175 V Corona : Loading via reflection: network.LuaLoader 01-26 20:57:45.762 21162 21175 I Corona : Platform: Moto G (4) / ARM Neon / 6.0.1 / Adreno (TM) 405 / OpenGL ES 3.1 V@139.0 (GIT@I1b38baa288) / 2017.3025 / English | US | en\_US | en 01-26 20:57:45.779 21162 21175 V Corona : \> Class.forName: shared.google.play.services.base.LuaLoader 01-26 20:57:45.780 21162 21175 V Corona : \< Class.forName: shared.google.play.services.base.LuaLoader 01-26 20:57:45.780 21162 21175 V Corona : Loading via reflection: shared.google.play.services.base.LuaLoader 01-26 20:57:45.813 21162 21175 V Corona : \> Class.forName: CoronaProvider.licensing.google.LuaLoader 01-26 20:57:45.813 21162 21175 V Corona : \< Class.forName: CoronaProvider.licensing.google.LuaLoader 01-26 20:57:45.816 21162 21175 V Corona : Loading via reflection: CoronaProvider.licensing.google.LuaLoader 01-26 20:57:45.825 21162 21175 V Corona : \> Class.forName: plugin.appnext.LuaLoader 01-26 20:57:45.825 21162 21175 V Corona : \< Class.forName: plugin.appnext.LuaLoader 01-26 20:57:45.826 21162 21175 V Corona : Loading via reflection: plugin.appnext.LuaLoader 01-26 20:57:45.873 21162 21175 I Corona : show scene now. 01-26 20:57:45.874 21162 21175 I Corona : show scene now. 01-26 20:57:52.037 21162 21175 I Corona : Received adLoaded for 342068f9-0810-4d19-81b8-1e6fd4a11a93\_interstitial with message 01-26 20:58:01.166 21162 21175 I Corona : Received adError for 342068f9-0810-4d19-81b8-1e6fd4a11a93\_interstitial with message no ads 01-26 20:58:06.575 21162 21175 I Corona : Received adError for d4706f6f-75ce-45a7-9e1c-3ccd32997c23\_fullscreen with message Error loading video 01-26 20:58:12.616 21162 21175 I Corona : Received adError for c93a6759-8bff-4e62-a87c-754a075b86cc\_rewarded with message Error loading video
I was told by Appnext that there are plenty of Ads for my region (Brazil, Sao Paulo) and on iOS it is actually working just fine.
I lost already quite some time trying to implement this plugin and/or waiting for an update, but it seems that Appnext (or Corona?) has no interest in resolving this problem 
Might this be related to the fact that this Ads plugin is free?
Felix
