I’m not a Renoise novice (I have a couple of years experience behind my belt and some record label releases coming out of pure Renoise-made material). However - and this is really embarrassing - I can’t work out why today of all days I’m getting sound out of only my left monitor and left headphone. This is undoubtedly something which is very simple to fix but I’ve had a few too many beers and I am perplexed at present. Any quick help would be appreciated - thank you!
Plug error?
At what point exactly does the sound go left channel? Is Renoise master output only showing left channel? Is your audio device only showing left channel?
This could be anything from asio config to driver error. Or even you having accidentally set the master pan. There are literally thousands of possibilities unless you are bit more specific and can trace the signal as it goes through the system.
Well, get Sober first, then pay attention to the Vu level meters:where in the chain are signals stereo and when do they become mono?
On that channel, inspect the panning of the channel and perhaps also other devices that contain a panning option (like the send-device).
Apologies for bothering you with this petty problem folks. It turns out that the headphone jack on my Focusrite 2i2 soundcard is only playing audio through one stereo channel. It was causing problems with other speakers I was working with because I was routing the audio from the headphone jack through a 1/4 inch stereo jack to dual 1/4 inch jack for the purposes of listening to my mix through speakers other than those from the main outputs. LONG STORY SHORT: my audio interface’s headphone jack is busted up 
Thanks for commenting anyway guys!