java.lang.NullPointerException: Cannot invoke "java.sql.Connection.prepareStatement(String)" return value null

Question

I'm fairly new to programming and trying to connect to a DB using HTML, I'm using Wildfly, Apache NB and Derby in this case, hosted locally, the thing is that the browser gives me the following error after I try to log in with the credentials that I have created in the DB: [Login screen1

Error

java.lang.NullPointerException: Cannot invoke "java.sql.Connection.prepareStatement(String)" because the return value of "model.Conexion.getConexion()" is null

So I went to NB Conexion.java to check the getter but I cannot seem to find what is the issue here is the code.

Also, I have tried this with different versions of JDK, JRE more specifically u144 and u271 tried with GlassFish5, Payara and Wildfly and still no luck.

I would really appreciate any help on this as my semester depends a lot on this

package model;

import java.lang.reflect.InvocationTargetException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;

public class Conexion {

    private static Conexion conexion;
    private static final String BDURL= "jdbc:derby://localhost:1527/proyectohtml;user=ROOT;password=1234";
    private static Connection conn;

    private Conexion(){
        try {
            Class.forName("org.apache.derby.jdbc.ClientDriver").getDeclaredConstructor().newInstance();
            conn=DriverManager.getConnection(BDURL);
        } catch (ClassNotFoundException | NoSuchMethodException | SecurityException | InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException | SQLException ex) {
            Logger.getLogger(Conexion.class.getName()).log(Level.SEVERE, null, ex);
        }    
    }

    public static synchronized Connection getConexion() {
        if (conexion==null) {
            conexion=new Conexion();
        }
        return conn;
    }
}