Sorry you’re having difficulty. I’m not familiar with the FireFace, but I would recomend you try these steps.
(and I’ll appologize in advance if some of them seem silly or redundant, I’m just working off of our trouble-shooting checklist!)
Verify signal from the guitar (pick up works, volume up etc)
Verify signal continutiy through the cord and any gear you have in line like stomp boxes
(if your interface has an ‘input signal’ indicator and if that indicator is responding, you can consider steps one and two complete.
Verify that the input on your interface is turned up (or at least not turned all the way down)
Open the Devices menu and then select “Device set up”. Make sure you ASIO driver is (still) set to your interface and not to “internal”. While your in there, double check that the input mapping clock setting is configured the way you want it. (clock issues as you probably know can cause all kinds of weird stuff).
Open the Devices menu again and select “VST connections”, go to the inputs tab and verify that the hardware port you want is still mapped to the input bus you’re using in your project. Some times I’ve been able to clear glitches by deleteing the input bus and then createing a new one. Sometimes that process seems to 'wake things up"?
Make sure that over on the outputs tab, your stereo out is still mapped to where you want it to go. (don’t know if you have the option to use the Control Room or not on your version… if you do have that ability, recommend you diable it until we get the rest of this sorted out)
Note: once you get everything squared away, I’d recommend you save your set up as a preset, that way you can just reload it in the future to clear any glitches etc.
Finally go back into your project, make sure the audio track input is mapped the input you want (again, try turning that connection off and back on).
Let me know where you come out!