That fixed it; thanks!
I see this now in the Spike FAQ – but Spike wasn’t giving the quoted error and TGStandalone isn’t Spike. It’s also listed as “SA44/SA124 only”. I did actually go through the Spike FAQ and saw this before I started this thread, but did not try it because it didn’t apply to my situation thrice over.
It’s also not on the USB-TG44A Product Page and it’s not in the USB-TG44A User Manual.
Please consider making this important little nugget easier to find!