Automation Action - config form keeps spinning, no request is sent to the app's server, what am I doing wrong?

I am trying to create Automation Action using following module:

"automationActions": [
      {
        "key": "apply-template-action",
        "name": {
          "value": "Apply template"
        },
        "configForm": {
          "url": "/render/automation-action-edit?projectKey={project.key}"
        },
        "webhook": {
          "url": "/apply-template"
        }
      }
    ]

However, I can’t make the form to appear:

Action is visible, but nothing happens after I select the option. Spinner keeps spining. I don’t receive any requests on the server side. However, I do see a strange error in the network tab:

How do I make it work?

Today I’ve checked sample app: jira-servicedesk-hipchat-action

It is not working either, so I am assuming the feature is broken.