Also check proper connection (View/Connections...) for your mono source (eg. mic, guitar) into the new input bus port (eg. Mono/in).
Assign the newly created bus ("Mono") as input to the audio track you're about to record into (see Track/Track properties...). Note that you can leave the track's output bus to stereo (ie. default "Master", channels = 2). This way all recorded audio files in this rack will be mono while playback will get rendered (ie. duplicated) to a stereo bus.
You'll need a mono audio input bus. Create one Audio Bus (see View/Buses...) as follows for example:
Mode: Input
Channels: 1
Auto-connect: yes
Also check proper connection (View/Connections...) for your mono source (eg. mic, guitar) into the new input bus port (eg. Mono/in).
Assign the newly created bus ("Mono") as input to the audio track you're about to record into (see Track/Track properties...). Note that you can leave the track's output bus to stereo (ie. default "Master", channels = 2). This way all recorded audio files in this rack will be mono while playback will get rendered (ie. duplicated) to a stereo bus.
HTH