Slack bot unreachable ngrok in the development mode

Question

I am writting the slack bot using @slack/bolt. I am trying to configure the development mode using ngrok. The problem is that a couple of weeks ago everything worked perfectly fine, but now, my ngrok became just unreachable.

So, here is what I am doing step-by-step when trying to start the application in the development mode:

1. ngrok http 3000
2. Then, I start my application on port 3000. Ngrok generates for me this URL:

Forwarding                    https://8a04-37-47-197-5.eu.ngrok.io -> http://localhost:3000

3. I copy this URL, add /slack/events, as @slack/bolt documentation says and paste this URL into the Slack application (https://8a04-37-47-197-5.eu.ngrok.io/slack/events) for the event subscriptions.

And here is where the problem starts. Once I paste this URL, it returns this error: Your URL didn't respond with the value of the challenge parameter. The most interesting thing is that I don't have even any logs in the ngrok console.

Also, if I send the request manualy via curl, at least I see logs. For example: curl -X POST https://8a04-37-47-197-5.eu.ngrok.io/slack/events at least will show me the 401 status code. What is wrong? It worked just a couple of weeks ago.