Couldn't send test push notification message

I was trying to send test push notification from the dashboard. But I got an error - Failed to get push result.

It looks like an unhandled error condition. The Ajax call returns http status 500 and a general error payload

{
    "message": "Failed to get push result.",
    "error": true
}

Have you ran into similar situation before? I appreciate any help.

Hello,

I saw you asked about the same issue via our dashboard.
So I answered the issue and am waiting for your feedback.

Kind regards,
Brian