BUILD ERROR unable to start adb server please help me

in bulid settings when i build android game ,it is showing the error like this .please help me

I had encountered the same error. I tried the following and it worked:
1)Go to command prompt

  1. Go to android sdk folder (To know the current path of the android sdk go to edit->preferences in your unity project and then copy the path for android sdk )

3)Now navigate to platform tools folder in the android sdk folder and execute the following commands-

  1. set ADB_TRACE = 1
  2. adb start-server

Basically this error happens when the ADB server is not started properly

problem fixed here : Unity 2020 Android Support: Setup, SDK & NDK & JDK & Gradle - YouTube