404 Workflow with id ‘wf_6xx’ not found

This is my code next js

import { NextResponse } from 'next/server';
import OpenAI from 'openai';

export async function POST() {
  if (!process.env.OPENAI_API_KEY) {
     return NextResponse.json({ error: 'OPENAI_API_KEY is not set' }, { status: 500 });
  }

  const openai = new OpenAI({
    apiKey: process.env.OPENAI_API_KEY,
  });

  try {
    const workflowId = process.env.OPENAI_WORKFLOW_ID || "default";

    // Create a session using the beta ChatKit API
    // The previous implementation used openai.chatkit which is undefined
    const session = await openai.beta.chatkit.sessions.create({
        user: "user-123", // Replace with actual user ID from your auth system
        workflow: { id: workflowId },
    });
    
    return NextResponse.json({ client_secret: session.client_secret });
  } catch (error: any) {
    console.error('Error creating ChatKit session:', error);
    return NextResponse.json({ error: error.message || 'Failed to create session' }, { status: 500 });
  }
}

And i got this

{“error”: “404 Workflow with id ‘wf_6xx’ not found.”}