According to your question, there might be many reasons behind...
Check out this Stack Overflow Solution if this can work.
Apart from this, To remove Kotlin support you can check your Gradle for some lines below..
buildscript {
ext.kotlin_version = '1.2.71'
...
dependencies {
...
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
}
}
...
apply plugin: 'kotlin-android'
...
android{
...
sourceSets {
main.java.srcDirs += 'src/main/kotlin'
}
...
}
dependencies {
implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
...
}
Delete all of these above to remove kotlin support in your project.