Unable to re-configure slack bot

Thank you for developing such a wonderful product.

I have changed url of my self-hosted redash so I’d like to re-configure redash slack bot.
But redash slack bot doesn’t response to ‘start setup’ so I cannot update configuration.
The situation didn’t change even if I removed slack app and installed it again.
Slack bot responds to other words and queries.

Do you know any idea about how to re-configure slack bot?

Thanks,
Yu