Else If statement in Kotlin does not execute

I'm just starting with Kotlin. This code doesn't give off errors. But I don't get the output I need. The else if statement seems to get no effect, even if I don't enter any character in the field. What did I do wrong?

fun main(){
    print("Enter First Name: ")
    var firstname: String? = readLine()
    print("Enter Last Name: ")
    var lastname: String? = readLine()
    print("Prefix (Ms/Mr/Mrs)?: ")
    var prefix: String? = readLine()

    if (prefix!!.contains(".")){
        prefix = prefix.substring(0,prefix.length-1)
    }

    if (firstname!!.isNotEmpty() && lastname!!.isNotEmpty() && prefix.length != 0) {
        println(Applicant(firstname,lastname,prefix).message)

    }
    else
        if (firstname == "\n"){
            println("The First Name field is empty. Re-run the program to try again.")
    }
        if (lastname == "\n"){
            println("The Last Name field is empty. Re-run the program to try again.")}


}