Latest news in the portal science: append /_service/about to your portal URL in the latest release of Dynamics 365 Portals to get the handy ‘Clear cache‘ button.

Portals clear cache button

It’s a heavy-duty tool and should be used in production as a last resort only (but developers – rejoice!). If change tracking does not work for you, I still recommend figuring out why and raising a support request with Microsoft if required.