Updated to Android Studio 3.0. Getting a "Kotlin not configured" error

In Android Studio, click on File -> Invalidate Caches / Restart... , then select "Invalidated and Restart". This solved my problem.

Closing and restarting Android Studio works for me in that case. Important is that there are no other projects opened in Android Studio before you close it. I suspect that closing Android Studio with multiple opened project windows sometimes messes up the configuration especially after plugin upgrades etc.

This error also occurs if you have the mavenCentral() repository missing in allprojects. Your build.gradle (:app) should contain at least this:

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}

jcenter() would work as well (for now), but that repository reached end-of-life and shouldn't be used any more.

I first tried with invalidate cache/ restart option but it doesn't help me.

When I updated Kotlin to 1.1.60 in project's gradle file, problem is solved.

Also, use this in app's gradle for stdlib

implementation "org.jetbrains.kotlin:kotlin-stdlib:1.1.60" 

instead of

implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:1.1.60"