What does "Currently you can add only one rule like this" in message trigger rules mean?

I am trying to create a Chat message that will be sent 3 days after some event happened for the first time. I think that I was able to set up such message yesterday using “Add event or rule date” button.

However, today the button is grayed out and when I hover over it, it says “Currently you can add only one rule like this”.

What does that mean? It this function temporarily disabled globally? Or is there some problem with our account setting or something? When will be this feature available again?

I cannot see any ongoing incident on https://www.intercomstatus.com/ . Neither I can see any note in the documentation (https://www.intercom.com/help/en/articles/5420235-send-messages-on-a-recurring-schedule and https://www.intercom.com/help/en/articles/5180516-send-repeatable-messages-based-on-events-you-track-in-intercom) that the feature is available only in some specific cases.