How to configure redash bot in slack?

Recently I added Redash to Slack and as far as I know or understood in Redash information, after adding Redash to Slack I must have a bot message like this: (Step 2)

This is what I get:

But I didn’t get the message and I’m unable to use the “/redash” command due to “Bot not configure Yet”.
I followed the steps and I don’t know what I did wrong, I hope if anyone could help because we have to share some reports.

Also, I have a problem with the Pivot Table Dates, it seems that each date is converted into another format. When I create a pivot table from my data all my integer values are in other format. This is what I get in my pivot table, and I want it in YY-MM-DD format.

Is your Redash instance accessible over the public internet? It needs to be in order for Slack to communicate with it.