Sometimes it helps that the lane that is routed into the Virus is record-armed/monitored while you select the input source in VC. Also, maybe the source volume is too low and the effects you are running it through make it even lower so that you cannot hear it.
Hope this helps.
If you are trying to get the audio from a software instrument track into the Virus you will need to first send the software instrument tracks audio to a bus then use the bus as the source for the sidechain, this does not apply if you are working with audio tracks.
Ruari I'm trying to send an audio track into it a software instrument. I am right in thinking you can do this via USB?
Ok, yes you most certainly can route an audio track into your Virus, that's how you will make use of Atomizer (which you really must try out by the way 
). I was just trying to help you out by letting you know about one of Logics peculiarities in my last post, sorry for any confusion.
All you should need to do to set this up from an INIT patch is make sure your Virus is configured 3 outs / 1 input in the Config > Patch Utility page then select the required audio track from the sidechain menu in the top right of the plug in window, now click the FX 1 tab & under INPUT change the mode to Static, change the input to L + R & leave atomizer off for now.
If you just want to hear the processed audio from the Virus then change the audio channel strips output from Stereo Out to No Output then press play on the project, your audio should now be routed thru the TI & if you turn the filter resonance up and sweep the cutoff you should hear something happen.
If you want to take things a bit further then change the mode to Dynamic, turn the Filter Env Amount up alter the filter envelope to suit, select the Virus track in your arrange window, press play on the project and play some keys. From there you can experiment to your hearts content as there's plenty for you to discover - did someone say Vocoder…
To have some Atomizer fun then the best thing you can do now you know how to route audio into the Virus is read the Atomizer manual, expect to lose hours if not days once you do this as atomizing is highly addictive once you get going with it.
Hope this gets you up & running 
Thank you so much Ruari.
Finally i've managed to get audio running through the virus
Also just had a quick read up on the atomizer and sounds amazing!!!
Your directions worked perfectly although due to something called work i'm not able to play with everything you've mentioned but tomorrow is another day and i will definitely get back to you on how i've got on and if i have any more questions.
There is one thing i would like to ask now though, the audio is around a beat out of sync and is also distorted, is there anyway to amend these problems?
