Check if you have this in top of your app build.gradle?
apply plugin: 'kotlin-kapt'
add this line
if you used kapt in android library you must add kotlin-android plugin in your project
apply plugin: 'kotlin-android'apply plugin: 'kotlin-kapt'
just add this line in your app-level of build.grale :
NOTE: under apply plugin: 'com.android.application'
apply plugin: 'com.android.application'