Power filter board for Rpi does not work?

I’m using an iFI audio iPowerX with adapter socket from a circular power Jack into the Pi USB-C input and it has worked fine for several years as a media server running Volumio; when plugged into the new dfrobot power filter HAT power socket the lights on the Pi fire up for about a second and then slowly fade out. But back into USB-C it works fine.

Is it faulty?

I’ve written to the tech support email address but not received any reply so posting here for advice. My reseller (the Pi hut) says I need to ask dfrobot for a diagnosis before they refund or replace it.