We have set a date for the removal of the legacy AdMob plugin: on March 1, 2017, the AdMob V2 plugin, accessible under the namespace
plugin.google.play.services, will be officially retired and it will become unavailable for new Corona SDK and Corona Enterprise builds.
You should begin migrating all apps which use the legacy AdMob plugin over to the updated AdMob plugin, or alternatively explore other monetization solutions. Note that your apps currently available in various app marketplaces will continue to serve ads — this only impacts new builds and updates starting on March 1.
The updated AdMob plugin is available for $199/year in the Corona Marketplace. It is also bundled as part of the Corona Professional Bundle for $699/year which includes AdMob, Chartboost, AdColony, Unity Ads, and the Corona Splash Screen Control.
Please join us in the Corona forums to discuss these changes.