The "provider_token" parameter is necessary when sending an invoice through the Telegram Bot API. This token is used to authenticate and identify the provider (merchant) who is sending the invoice.
If you are receiving the error "Bad Request: parameter 'provider_token' is required" when trying to send an invoice with the provided token, it could be due to a few reasons:
1. The token you are using is incorrect or expired. Double-check the token and make sure it is copied correctly from the provider dashboard.
2. The provider (merchant) associated with the token does not have the necessary permissions to send invoices. Make sure that the provider account is properly set up and has the required permissions.
3. There may be a bug or issue with the Telegram Bot API. In this case, you can try reaching out to Telegram support for assistance.
Overall, the "provider_token" parameter is required for sending invoices through the Telegram Bot API, and ensuring that it is correct and properly configured will help resolve the error.