Sending message to private Telegram channel fails using Bot API python

I have tried sending message to a telegram channel using Telegram’s BOT API with Python 3.11.0.

At first I have tried making the channel Public and the code worked fine:

import requests

# Replace YOUR_BOT_TOKEN with your actual bot token
bot_token = BOT_API_KEY

# Replace YOUR_CHAT_ID with the chat ID of the recipient
chat_id = '@testme100'

# The message you want to send
text = 'Hello, world!'

# The URL for the Telegram Bot API
url = f'https://api.telegram.org/bot{bot_token}/sendMessage'

# The data to be sent in the POST request
data = {'chat_id': chat_id, 'text': text}

# Send the POST request
response = requests.post(url, data=data)

# Check the response status code
if response.status_code == 200:
    print('Message sent successfully.')
else:
    print(f'Error sending message: {response.text}')

The output:

But then I thought of making it private channel and changed the Channel ID:
The URL is : https://t.me/+vMjFCXBghv00NDZl and I thought the text ahead of + is the channel ID, so I changed the chat_id = '@vMjFCXBghv00NDZl'.

But now it’s not sending the messages to the channel. When I make it public again then it works fine.

The error I received = Error sending message: {"ok":false,"error_code":400,"description":"Bad Request: chat not found"}