Installing Dialogflow bot in Slack fails due to 'oath authorisation url mismatch'

Question

I've got a simple Dialogflowbot that I'm trying to integrate with my Slack workspace.

• I've made a Slack app for the bot.
• I've added all the information in Dialogflow integration dialog.
• On Slack app side I've set-up bot user, added event subscriptions (including link from DF) and set up OAuth scopes and added the URL.

However, the bot won't reply back. Everything looks fine in DF logs but I'm not getting responses in Slack. Previously I've been able to solve this kind of situation by clicking the 'Install to Slack' button under 'Manage distribution' -tab. However, now when I do that (and allow installation), I receive the following error message:

While starting bot the error appears:
Bot start error: oauth_authorization_url_mismatch

From Slack documentation I've found out that this means "The OAuth flow was initiated on an incorrect version of the authorization url. The flow must be initiated via /oauth/authorize." However, the OAuth URL Dialogflow provides is of form bots.dialogflow.com/slack/<TOKEN>/start.

I've

• contacted both Slack and Dialogflow support
• done bunch of Googling and
• asked a few people that also work on Slack bots

but I've found nothing. Maybe someone here would have ran to the same issue would know what to do?

Answer 1

Recently the Slack team made a change in the oauth authentication with backward incompatible changes. This change break the integration with Dialogflow.

Fortunately, the old functionality has not been fully removed from Slack. In the link I shared above (here's again), at the bottom of the documentation there's an option to "Create a classic Slack app". If you click on it, you will be able to create a "legacy" bot and use follow the Dialogflow-Slack integration guide; it will work as intended.

An important thing to notice, is that you'll see an option to "Update Scopes". Be careful not to make this update, as this will change the authentication from classic to the new approach, and it will break the bot.

Finally, the Dialogflow team already knows about this issue and they're working to make the integration compatible with the new Slack authentication. You can subscribe to that IssueTracker (click the star next to the title) and get updates regarding its progress.