Slack Interactive Messages: No POST response from Slack - node.js

Question

I'm constructing and sending the message attachment:
var zz = {
"text": "Would you like to play a game??",
"attachments": [
{
"text": "Choose a game to play",
"fallback": "You are unable to choose a game",
"callback_id": "wopr_game",
"color": "#3AA3E3",
"attachment_type": "default",
"actions": [
{
"name": "chess",
"text": "Chess",
"type": "button",
"value": "chess"
}
]
}
]
}
web.chat.postMessage(message.source.channel, '', zz);
The message with buttons displays fine on Slack, but when I tap a button there's no POST response from Slack to my local ngrok or express route:
app.post('/slackaction', function(req, res)
While other messages are posting fine to this route.
I'm seeing this error from Slack after I tap a button:
"Oh no, something went wrong. Please try that again"
Slack Interactive Messages request_url set as:
https://xxx.ngrok.io/slackaction

Answer 1

Thanks to comments from Taylor Singletary for pointing me in the right direction.
The test tokens or a bot token for Custom Integrations can post Interactive Messages but you need an App to handle them.
To fix it you need to add a bot to your app here: https://api.slack.com/apps
and then get the access token for that bot.
You can use the Slack button generator here: https://api.slack.com/docs/slack-button# to get the OAuth URL and paste it on a browser.
Then from your app handle the OAuth flow, store the access token and use that with chat.postMessage.
Then you should receive the POST request when clicking on the message buttons.