A week ago we we reported that Google has new structured data named SpecialAnnouncement that some sites can use to markup their Google search results. Well, Google didn't write a blog post about it until Friday afternoon and it isn't live yet. Danny Sullivan of Google said it should be live soon.
So if you are wondering why your markup here doesn't work, it isn't fully live yet. Danny said it should be soon, here is that tweet:
I don't think yet but soon.
— Danny Sullivan (@dannysullivan) April 6, 2020
If you are wondering what it looks like, here is a sample screen shot from Google:
Forum discussion at Twitter.