[SOLVED] Can't install Dialogflow integration

Previously I had the Dialogflow integration worked very well.
But yesterday my actions stopped working with Home Assistant. Google Assistant said that the HA can’t be reached. I’ve tried to check webhook and found that I can’t get the webhook URL. The ‘Configure’ option was absent in Dialogflow menu.
So I’ve decided to reinstall Dialogflow. I’ve unistalled it. But now I can’t install it back. I only see the error 'Unknown error occurred'.

Please help to identify the reason of this issue.

# Core
Version
core-2021.5.5

# Supervisor
Version
supervisor-2021.04.3

Fixed the issue with adding

homeassistant:
  external_url: "https://url"