Why Boolean value doesn't change its value in else snippet?

Why Boolean value doesn't change its value in else snippet, since overriding should happen in keepGoing variable in else body, what is the problem?

import java.util.Scanner;
public class Main {

    public static void main(String[] name) {
        Scanner display = new Scanner(System.in);
        StringBuilder check = new StringBuilder();
        boolean keepGoing = false;

        do{
        System.out.println("please insert your name to check if it is valid or not:");
        String Name = display.next();

            if(Name.equals("alex")) {
                System.out.println("it is valid");
                keepGoing = false;
            }


            else {
                System.out.println("it is not valid");
                System.out.println("do you want to continue: yes/no");
                check.append(display.next());
                keepGoing = check.equals("yes");
            }
        } while(keepGoing);


    }
}```