Aha. Turns out, with dual GI275s, only one is connected to the USB port. I was using the bottom device and should have been using the top device. Magic!
Just got “Airplane Engines - A Pilot Friendly Manual” from Pilot Workshops. This book has moved to the top of my list of Very Useful Engine Books. I own all the Mike Busch ones and other assortments but the Pilot Workshop Manual is just chock full of just what you need to know to pre-flight...
I have the new GI275 installed on my 172N. I have the Garman USB port available for updates but every time I try to plug in a USB stick with the current databases the GI 275 says USB device not found.
I’ve installed the USB stick before all the power was switched on, then searched after start...