I have just noticed something odd with my Prime 4…
When using a USB keyboard plugged into USB 1, the Prime 4 GUI does not respond to some of the keys. For example if I try to search for ‘fred everything’, the e doesn’t work, or the space bar.
I tried another keyboard and it worked normally (same USB socket).
I then plugged the “bad” keyboard into the USB 4 socket on the rear - and it worked normally.
Your FAQ states that a keyboard can be used in any USB socket.
Having now tried the “bad” keyboard back in the USB 1 port, it’s working correctly, as if plugging it into USB 4 somehow “woke up” Engine OS.
[later] Tried rebooting the Prime 4 and using USB 1 again. Keyboard initially worked, then suddenly started missing keys again. It seems to be related to the OSK.