Unable to convert classes into dex format

thats what the console says:
CommandInvokationFailure: Unable to convert classes into dex format.
C:/Program Files/Java/jdk1.8.0_121\bin\java.exe -Xmx2048M -Dcom.android.sdkmanager.toolsdir=“C:/Users/PEDRO/AppData/Local/Android/sdk ools” -Dfile.encoding=UTF8 -jar “C:\Program Files\Unity\Editor\Data\PlaybackEngines\AndroidPlayer/Tools\sdktools.jar” -

stderr[
Uncaught translation error: java.lang.IllegalArgumentException: already added: Lcom/unity3d/ads/BuildConfig;
Uncaught translation error: java.lang.IllegalArgumentException: already added: Lcom/unity3d/ads/IUnityAdsListener;
Uncaught translation error: java.lang.IllegalArgumentException: already added: Lcom/unity3d/ads/UnityAds;
Uncaught translation error: java.lang.IllegalArgumentException: already added: Lcom/unity3d/ads/UnityAds$1;
Uncaught translation error: java.lang.IllegalArgumentException: already added: Lcom/unity3d/ads/UnityAds$2;
Uncaught translation error: java.lang.IllegalArgumentException: already added: Lcom/unity3d/ads/UnityAds$FinishState;
Uncaught translation error: java.lang.IllegalArgumentException: already added: Lcom/unity3d/ads/UnityAds$PlacementState;
Uncaught translation error: java.lang.IllegalArgumentException: already added: Lcom/unity3d/ads/UnityAds$UnityAdsError;
Uncaught translation error: java.lang.IllegalArgumentException: already added: Lcom/unity3d/ads/adunit/AdUnitActivity;

UNEXPECTED TOP-LEVEL EXCEPTION:
java.lang.RuntimeException: Translation has been interrupted
at com.android.dx.command.dexer.Main.processAllFiles(Main.java:613)
at com.android.dx.command.dexer.Main.runMonoDex(Main.java:311)
at com.android.dx.command.dexer.Main.run(Main.java:277)
at com.android.dx.command.dexer.Main.main(Main.java:245)
at com.android.dx.command.Main.main(Main.java:106)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at SDKMain.main(SDKMain.java:129)
Caused by: java.lang.InterruptedException: Too many errors
at com.android.dx.command.dexer.Main.processAllFiles(Main.java:605)
… 9 more
]

Solved:I downloaded this Unity Asset Store - The Best Assets for Game Making and unnistalled UnityAds.

Android Jar Dependencies
“Replace play-service-ads-lite version 10.2.6 with version 11.0.4”

When I opened my project after long time I got this popup,
I ignored it and build the game but it gave the
“Unable to convert classes into dex format build error”.

I restarted unity and REPLACED the play service ads lite version
as the popup came again and it SOLVED MY PROBLEM… :smiley: