Our current site (web.miniextensions.com) does not use an API key at all since the connection is established in an entirely different manner (OAuth).
Users of our legacy site (app.miniextensions.com) need to switch to the Personal Access Token system as explained in this article.
If the connection to Airtable has been revoked for some reason you will need to reconnect your Airtable integration on the settings page. Select the correct workspace on the left and then scroll down to the bottom of the page and reconnect your Airtable integration.