How do you troubleshoot a WebGL Build Error?

UnityEditor.BuildPlayerWindow+BuildMethodException: 4 errors at UnityEditor.BuildPlayerWindow+DefaultBuildMethods.BuildPlayer (BuildPlayerOptions options) [0x0020e] in /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs:181 at UnityEditor.BuildPlayerWindow.CallBuildMethods (Boolean askForBuildLocation, BuildOptions defaultBuildOptions) [0x00065] in /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs:88 UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

Here's what I've tried so far

downloading a different older and newer version of unity 2017.3,2018.1,2018.3 I've transferred just the assets to a new project --same error. I've tried to restart computer and unity