As far as I can see the app can only connect via WiFi or Ethernet LAN. Did you check the User Guide or Help section of the app for troubleshooting steps regarding device discovery and pairing?
I have confirmed that the error message only appears the graphics driver is not installed. Did you install the driver before upgrading to Windows* 8.1 Enterprise?
I performed a fresh install of 8.1 Enterprise. I have the Intel HD Graphics driver installed, ver. 10.18.10.4226.
It would be nice if we could encourage Intel to develop the keyboard app to allow pairing via Bluetooth. We cannot pass through this traffic as our APs drop the traffic. Which, obviously requires the stick connected via WiFi and we are using these with USB-to-Ethernet dongles.
**EDIT: Trying to re-install graphics drivers. Otherwise, I'll just pull the keyboard app until there's a fix and/or there's a Bluetooth function.
***EDIT" Driver re-install did not resolve the issue.