Team Calendar is blank when using K15T's Scroll Viewport

[Angela L_]

I'm using the Team Calendar macro (subscribed by URL) on a page in Confluence (Data Center 8.5.4). The calendar has lots of events on it, and they all show up as expected in Confluence.

But when I view that same page through Scroll Viewport, the calendar appears with zero events on it. Why?

(On K15T's documentation for which macros they support or don't, the Team Calendar macro isn't even acknowledged despite that page listing other macros they don't support.)