There is a problem related to Rewarded ads's callbacks. That's if the rewarded ad is loaded from MoPub mediation network, then the ad callbacks and onUserEarnedReward are not triggered properly (note that everything is working properly with ads from AdMob).
02-28 13:25:49.864 10405 17806 17806 I Ads : This request is sent from a test device.
02-28 13:25:50.058 10220 24853 28873 I Ads : SDK version: afma-sdk-a-v204204999.204204000.1
02-28 13:25:50.060 10220 24853 28873 I Ads : HTTP timeout: 60000 milliseconds.
02-28 13:25:53.528 10405 17806 17806 D MoPubMediationAdapter: Showing a MoPub rewarded video.
02-28 13:25:53.534 1000 1244 6203 I ActivityTaskManager: START u0 {flg=0x10000000 cmp=com.admobtestapp/com.mopub.mobileads.MoPubFullscreenActivity (has extras)} from uid 10405
// watched 30s video ad -> onUserEarnedReward is not called
// pressed BACK to close ad
02-28 13:26:36.771 10064 4483 28252 I TrayUsageStatesWatcher: noteResumeComponent : ComponentInfo{com.admobtestapp/com.admobtestapp.AdsActivity}, 4
02-28 13:26:36.778 10405 17806 17806 D admobtestapp: AdsActivity: onResume