I’ve done a little more digging, but too late to do much else tonight.
From a cold start, the fans are spinning. But they don’t stay spinning, and keep coming to a stop.
I installed the EVGA XP1 software, and it allows for more granular control over the fans, including response curves. It seems to ignore them.
At lower temperatures, the fans will spin, but if I set it to say 100% the fans will very briefly spin up to 3500rpm, but for only half a second, then come to a full stop. If I set them to a lower speed it seems to work okay briefly, but eventually the temperature rises till it gets to a point where the fans just power off.
I’ll take the card out tomorrow to give it an inspection for debris or other obstructions. But the fans don’t appear to be dead,can’t perhaps more an issue with the fan controller.