Thanks for all the responses. Everything has been power cycled multiple times, and in reverse order. The Aries and Mk2 were powered off when I changed connections, powered Mk2 first and was then told by Aries that the selected output (which had been USB) was not available with my device. I checked all the settings, multiple times but, again, the problem is not limited to one device (I’ve tried four, so far). My microRendu is already on 2.8 OS. MacBook Pro is running Monterey, not that that should matter. I suspect Vince and dawkinsj are right that it is probably a hardware issue, or maybe a software problem (could it be a bad firmware load–I haven’t changed anything with the firmware since I got it?). When I get my second Mk2 (I’m probably well behind you, emailists), if it works I’ll have a better idea. Still waiting to hear back from PSA support. For now I’ll just stick with the Matrix and IS2.