The Kotlin compiler automatically generates setters and getters for the field.
But you are using the @JvmField annotation.
This annotation instructs the Kotlin compiler not to generate getters/setters for this property and expose it as a field. Kotlin Documentation link.
If you are using only Kotlin classes and do not extends from Java classes, you most likely do not need this annotation.
If you remove this annotation everything should work fine.
In special cases, you may need to define special getters in java-extended entities, for this, see another Kotlin Documentation link.