I checked Log, it seems some cross reference issue with Firebase Analytics and Google Play Services,
As per Log When you call Show Ads Method, Its Start to create the view and trying Display Ads, at the same time (maybe in the separate thread) Firebase SDK also try to sent envent to server. during that it will going to crash
I/Unity (13331): lan choi thu : 4
I/Unity (13331):
I/Unity (13331): (Filename: ./artifacts/generated/common/runtime/UnityEngineDebugBindings.gen.cpp Line: 42)
I/Unity (13331):
I/Unity (13331): ShowAd
I/Unity (13331):
I/Unity (13331): (Filename: ./artifacts/generated/common/runtime/UnityEngineDebugBindings.gen.cpp Line: 42)
I/Unity (13331):
I/Unity (13331): Da show ad
I/Unity (13331):
I/Unity (13331): (Filename: ./artifacts/generated/common/runtime/UnityEngineDebugBindings.gen.cpp Line: 42)
I/Unity (13331):
V/ContextImpl(13331): ----- packageName = com.sg.bubblepopstory is NOT LOCKED -----
I/DualAppsService( 446): OVERLAY- noOverlay=com.sg.bubblepopstory
I/DualAppsService( 446): OVERLAY- noOverlay=com.google.android.gms.ads.AdActivity
I/ActivityManager( 446): START u0 {flg=0x80000 cmp=com.sg.bubblepopstory/com.google.android.gms.ads.AdActivity (has extras)} from pid 13331
E/IMGSRV ( 172): :0: PVRDRMOpen: TP3, ret = 63
D/dalvikvm( 446): GC_FOR_ALLOC freed 1632K, 22% free 24840K/31540K, paused 64ms, total 65ms
W/AppLockService(13591): topActivity = com.sg.bubblepopstory PreviosActivity = com.google.firebase.MessagingUnityPlayerActivity
After that, these lines may the point to crash reason is some FireBase code (I am not the expert Android coder or never work with FireBase SDK So I guess it)
W/InputDispatcher( 446): channel '21eab208 com.sg.bubblepopstory/com.google.firebase.MessagingUnityPlayerActivity (server)' ~ Consumer closed input channel or an error occurred. events=0x9 E/InputDispatcher( 446): channel '21eab208 com.sg.bubblepopstory/com.google.firebase.MessagingUnityPlayerActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
E/OMXNodeInstance( 183): !!! Observer died. Quickly, do something, ... anything...
D/dalvikvm( 446): GC_FOR_ALLOC freed 1020K, 20% free 25530K/31540K, paused 52ms, total 52ms
W/AudioService( 446): AudioFocus audio focus client died
I/AudioService( 446): AudioFocus abandonAudioFocus(): removing entry for android.media...@21cbbca8com.google.android.gms.ads.internal.overlay.au@21c50678
V/KeyguardUpdateMonitor( 446): handleSetGenerationId(g=57, clear=true)
D/Sensors ( 446): alp : AccelSensor setEnable, handle = 0, flags = 0, mEnabled = 1
D/Sensors ( 446): alp : ID_A open, fd = 272 E/Sensors ( 446): alp setDelay : SENSOR_NOPOLL!!!
W/InputDispatcher( 446): Attempted to unregister already unregistered input channel '21eab208 com.sg.bubblepopstory/com.google.firebase.MessagingUnityPlayerActivity (server)'
I/WindowState( 446): WIN DEATH: Window{2207bc50 u0 com.sg.bubblepopstory/com.google.android.gms.ads.AdActivity}
I/WindowState( 446): WIN DEATH: Window{21ef1a88 u0 SurfaceView}
I/WindowManager( 446): Screenshot Window{2207bc50 u0 com.sg.bubblepopstory/com.google.android.gms.ads.AdActivity EXITING} was all black! mSurfaceLayer=21030 minLayer=21030 maxLayer=21030
I/WindowState( 446): WIN DEATH: Window{21eab208 u0 com.sg.bubblepopstory/com.google.firebase.MessagingUnityPlayerActivity}
D/dalvikvm( 446): GC_FOR_ALLOC freed 1105K, 22% free 24805K/31540K, paused 45ms, total 45ms
May it will help you.