Telegram Bot "chat not found"

If your trying to send messages to a group, you must add a ‘-‘ in front of your chat ID. For example:

TELEGRAM_REG_CHAT_ID="1949275XX"

should be

TELEGRAM_REG_CHAT_ID="-1949275XX"

As @maak pointed out, you need to first send a message to the bot before the bot can send messages to you.

I was using prefix @ before the value of chat_id as suggested everywhere. I removed it and it started working. Note: if your chat id is 12345678 then you need to prefix it with -100 such that it is -10012345678. Example Postman call:

/sendMessage?chat_id=-10012345678&text=Let's get together