VooDoo - Are you talking about the channel with the backing track only or the channel with both the backing track and your solo? Check to see if you have muted that particular channel in Audacity. This would be the square box over at the left of the screen. I had the same problem but figured it out.
If else fails, close the program, then reopen it it. You will need to reload the backing track. I hope this helps.
Guitars:
Electric: Washburn HB-30, Squier Tele Custom Deluxe, Jay Turser Strat.
Acoustic: Seagull S6.
AMPs: VOX AD30VT, Peavey Envoy 110.
Modelers: V-AMP 2, Digitech RP-100A.
Pedals: Boss RC-2 Loop Station, Boss CE-5 Chorus Ensemble, Digitech Bad Monkey, Ibanez DE7 Delay/Echo, DOD VFX40B 7-Band Graphic EQ, Ibanez CS-5 Super Chorus.