I am Not able to connect my .crt and .key file to Azure IoT Hub, it give connection error while my file path and host is correct

Question

import os
import asyncio
from azure.iot.device.aio import IoTHubDeviceClient
from azure.iot.device import X509

x509_cert = X509(
    cert_file="E:\\Repo\\RRR_1.crt",
    key_file="E:\\Repo\\RRR_1.key"
    # cert_file="20003C_1.crt",
    # key_file="20003C_1.key",
)

async def main():
    # Fetch the connection string from an environment variable
    # conn_str = os.getenv("IOTHUB_DEVICE_CONNECTION_STRING")

    # Create instance of the device client using the authentication provider
    device_client = IoTHubDeviceClient.create_from_x509_certificate(device_id='RRR_1',hostname='monoiothub.azure-devices.net',x509=x509_cert)

    # Connect the device client.
    
    await device_client.connect()

    # Send a single message
    print("Sending message...")
    await device_client.send_message("This is a message sent")
    print("Message successfully sent!")

    # finally, shut down the client
    await device_client.shutdown()


if __name__ == "__main__":
    asyncio.run(main())