Talk to @botfather and disable the privacy mode.
More Related Contents:
- How to obtain the chat_id of a private Telegram channel
- How to obtain Telegram chat_id for a specific user?
- How to receive messages in group chats using telegram bot api
- How to solve disturbance in my bot in c#?
- How do I add my bot to a Telegram channel?
- Telegram Bot – how to get a group chat id?
- How do I download a file or photo that was sent to my Telegram bot?