Android SDK error - CommandInvokationFailure,Unity Android SDK Error - Commandinvokationfailure

I am trying to develop android apps using Unity, but there is an error.(CommandInvokationFailure)

How should I fix it?,I am using Unity to develop android apps, but there is an error on Android SDK.
It sais CommandInvokationFailure - Unable to list target platforms.
What should I do to fix it?

Refer to https://answers.unity.com/questions/1448148/android-sdk-error-commandinvokationfailureunity-an.html