I’ve had my UR-RT2 & Cubase for some time and have used all the ports for various bus inputs…
Today however I find that although line 3 & 4 show as active within “Audio Devices” in Cubase 13, when I go to “Audio Connections” and “Add Bus” it only gives me a mono or stereo option and stereo option just creates a bus with inputs 1 & 2 and I can’t change them.