Left and right bus disappeared from stereo options

Last week I created a project and added several stereo tracks, and when selecting the bus, could see left and right as options, as I’m using a Steinberg UR12 with two channels.
This week, I intended to create more tracks but I suddenly can’t see the left and right channels as options. I can only pick “Stereo” but can’t actually choose the right input channel - the options have disappeared. However, the buses are sep up right in Cubase, and if I duplicate the tracks from last week, the configuration with the options remains. I just can’t see the channels when creating a new track.
Any ideas??? I’m so lost here! I’ve tried everything

Hello and welcome.

I am under the impression that a Left Right option is only available for output busses, not for input busses.
If you need mono input busses you can simply create them by adding a bus (in Audio Connections) and set its configuration to mono.