Android Export Problem

I have a Problem to export a apk for android
i tried different settings and tutorials but nothing worked

here is a part from the log

UATHelper: Packaging (Android (ETC1)): Copying new .so F:\Unreal Projekte\TKCoach417\Binaries\Android\ file to jni folder…
UATHelper: Packaging (Android (ETC1)): UEDeployAndroid.RunCommandLineProgramWithException: Preparing native code for debugging…
UATHelper: Packaging (Android (ETC1)): Program.Main: ERROR: AutomationTool terminated with exception: ERROR: D:/Program Files (x86)/Android SDK/android-ndk-r12b/ndk-build.cmd failed with args APP_ABI="arm64-v8a " NDK_DEBUG=1
UATHelper: Packaging (Android (ETC1)): Program.Main: AutomationTool exiting with ExitCode=1 (Error_Unknown)
UATHelper: Packaging (Android (ETC1)): BUILD FAILED
PackagingResults: Error: Unknown Error

i have NDK r12b , ant 1.8.2 , jdk 1.8.0_77 installed

i think its a problem with the ndk,but i have no clue what to do :confused:

Thx for help