Message cards not showig on IPhone

Hi,

Since version 4.15.1 was rolled out to iPhone users message card are not shown. The cards shows as expected on desktop and android. They are running iOS 15.6.1. The cards are sent via webhooks and even a simple card like below is not working. What can that possibly be?

//Oscar

{
  '@context': 'https: //schema.org/extensions',
  '@type': 'MessageCard',
  'themeColor': 'ffda3e',
  'title': 'Test',
  'summary': 'Test',
  'sections': [
        {
      'startGroup': true,
      'facts': [
                {
          'name': 'Fact 1',
          'value': 'Yehaa',
                },
                {
          'name': 'Fact 2',
          'value': 'Do it',
                },
            ],
        },
        {
      'text': '## Test heading',
        },
    ],
}

Not working on iPhone:

Not showing on IPhone

Works on android and desktop: