Gmail Inbox Actions Missing?

Gmail used to display actions directly in the inbox, like "Check In Now" for a flight reminder or "View this Pull Request" for a GitHub email. Here is a page describing the feature: https://postmarkapp.com/guides/improve-your-transactional-emails-with-gmail-inbox-actions

I looked through my inbox and noticed that there are no inbox action buttons displayed. I didn't turn them off, so I am not sure what happened. This is in multiple accounts, devices, and browsers