Kotlin Koans with EduTools plugin: "Failed to launch checking"

Maybe could try IntelliJ Idea Edu which comes already bundled with EduTools.

In my case I had a problem related to JDK 11 and I had JDK 8 installed. This is how I fixed the problem:

Go to Settings / Build, Execution, Deployment / Build Tools / Gradle. At Gradle JVM select JDK 11 path.

It worked for me.

I found the problem in IDE logs as @NullReference suggested.

INFO - ecker.gradle.GradleCommandLine - Failed to launch checking 
Cannot run program "./gradlew" (...) No such file or directory

I had configured the project (Settings / Build, Execution, Deployment / Build Tools / Gradle) to use a local Gradle distribution and it seems that EduTools plugin always looks for the Gradle Wrapper, so I just had to generate a Wrapper for project and configure it to use my local Gradle distribution:

gradle wrapper --gradle-distribution-url file:///path/to/local/gradle-4.6-all.zip