I couldn’t understand why this URL “http://localhost:3000/api/orders/income” is responding with empty array [ ]

order.js (router)
Other functions such as create order, delete order, get orders from MongoDB database works perfectly but //GET MONTHLY INCOME Part is not working. Can anyone please fix this problem??

const Order = require("../models/Order");
const {
  verifyToken,
  verifyTokenAndAuthorization,
  verifyTokenAndAdmin,
} = require("./verifyToken");

const router = require("express").Router();

//CREATE

router.post("/", verifyToken, async (req, res) => {
  const newOrder = new Order(req.body);

  try {
    const savedOrder = await newOrder.save();
    res.status(200).json(savedOrder);
  } catch (err) {
    res.status(500).json(err);
  }
});

//UPDATE
router.put("/:id", verifyTokenAndAdmin, async (req, res) => {
  try {
    const updatedOrder = await Order.findByIdAndUpdate(
      req.params.id,
      {
        $set: req.body,
      },
      { new: true }
    );
    res.status(200).json(updatedOrder);
  } catch (err) {
    res.status(500).json(err);
  }
});

//DELETE
router.delete("/:id", verifyTokenAndAdmin, async (req, res) => {
  try {
    await Order.findByIdAndDelete(req.params.id);
    res.status(200).json("Order has been deleted...");
  } catch (err) {
    res.status(500).json(err);
  }
});

//GET USER ORDERS
router.get("/find/:userId", verifyTokenAndAuthorization, async (req, res) => {
  try {
    const orders = await Order.find({ userId: req.params.userId });
    res.status(200).json(orders);
  } catch (err) {
    res.status(500).json(err);
  }
});

// //GET ALL

router.get("/", verifyTokenAndAdmin, async (req, res) => {
  try {
    const orders = await Order.find();
    res.status(200).json(orders);
  } catch (err) {
    res.status(500).json(err);
  }
});

// GET MONTHLY INCOME  <-----

router.get("/income", verifyTokenAndAdmin, async (req, res) => {
  const date = new Date();
  const lastMonth = new Date(date.setMonth(date.getMonth() - 1));
  const previousMonth = new Date(new Date().setMonth(lastMonth.getMonth() - 1));

  

  try {
    const income = await Order.aggregate([
      { $match: { createdAt: { $gte: previousMonth } } },
      {
        $project: {
          month: { $month: "$createdAt" },
          sales: "$amount",
        },
      },
      {
        $group: {
          _id: "$month",
          total: { $sum: "$sales" },
        },
      },
    ]);
    res.status(200).json(income);
    
  } catch (err) {
    res.status(500).json(err);
  }
});

module.exports = router;

Order.js (module)
This is the Order.js module

const mongoose = require("mongoose");

const OrderSchema = new mongoose.Schema(
  {
    userId: { type: String, required: true },
    products: [
      {
        productId: {
          type: String,
        },
        quantity: {
          type: Number,
          default: 1,
        },
      },
    ],
    amount: { type: Number, required: true },
    address: { type: Object, required: true },
    status: { type: String, default: "pending" },
  },
  { timestamps: true }
);

module.exports = mongoose.model("Order", OrderSchema);

index.js
In this part, I declared all the necessary routes along with the order route but I don’t know why only get “/income” part is not responding.

const express = require("express");
const app = express();
const mongoose = require("mongoose");
const dotenv = require("dotenv");
const userRoute = require("./routes/user");
const authRoute = require("./routes/auth");
const productRoute = require("./routes/product");
const cartRoute = require("./routes/cart");
const orderRoute = require("./routes/order");
const stripeRoute = require("./routes/stripe");
const cors = require("cors");

dotenv.config();

mongoose
  .connect(process.env.MONGO_URL)
  .then(() => console.log("DB Connection Successfull!"))
  .catch((err) => {
    console.log(err);
  });

app.use(cors());
app.use(express.json());
app.use("/api/auth", authRoute);
app.use("/api/users", userRoute);
app.use("/api/products", productRoute);
app.use("/api/carts", cartRoute);
app.use("/api/orders", orderRoute);
app.use("/api/checkout", stripeRoute);
 
 const port = process.env.PORT;
 app.listen(port || 5000 , () => {

    console.log(`Backend server is running on port ${port}!`);
});

verifyToken.js

const jwt = require("jsonwebtoken");

const verifyToken = (req, res, next) => {
  const authHeader = req.headers.token;
  if (authHeader) {
    const token = authHeader.split(" ")[1];
    jwt.verify(token, process.env.JWT_SEC, (err, user) => {
      if (err) res.status(403).json("Token is not valid!");
      req.user = user;
      next();
    });
  } else {
    return res.status(401).json("You are not authenticated!");
  }
};

const verifyTokenAndAuthorization = (req, res, next) => {
  verifyToken(req, res, () => {
    if (req.user.id === req.params.id || req.user.isAdmin) {
      next();
    } else {
      res.status(403).json("You are not alowed to do that!");
    }
  });
};

const verifyTokenAndAdmin = (req, res, next) => {
  verifyToken(req, res, () => {
    if (req.user.isAdmin) {
      next();
    } else {
      res.status(403).json("You are not alowed to do that!");
    }
  });
};

module.exports = {
  verifyToken,
  verifyTokenAndAuthorization,
  verifyTokenAndAdmin,
};