If you're as big as I am (6'1", 240#), you will hate to do what I'm suggesting, but...
Crawl headfirst into the footwell with a flashlight and examine the clutch pedal all the way to the attachment point where the yoke and pedal mate up. Watch what happens as you depress the clutch pedal (last time I did this, I had to remove the seat or else risk injury to my back, so be warned if you are of the large persuasion or lack small friends). If the cable is loose or the yoke is unpinned, there's your problem.
Several things could have happened to the cable:
1. It failed - this happens, and sometimes a new clutch can require more pressure to function than an old cable will sustain. Time to buy new cable at the dealer. Was the pedal a lot firmer or harder to depress than the original? If so, you might have a problem with the clutch install, alignment of shafts, wrong parts (particularly seals and bearings - you did replace the throw-out bearing, right?), etc. It would be normal for the new clutch to require a bit more effort on the pedal than a worn-out item, but...
2. The attachment to the pedal fell off (if you removed it during the install, this is probably your fault). This is the dream solution, with nothing more than refitting the hardware or replacing a piece of hardware all thats needed to fix it. Its also possible that you dislodged the clutch adjuster mechanism or firewall mount, all of which needs to be eyeballed (more lower back pain!).
3. The attachment to the throw out arm fell off. This is actually likely to be the problem. If you can reach up and pull the cable out of the housing, this is it. Examine the cable's hardware on that end - if it looks ok, you just have to reattach everything (easy for me to say, of course, my back's still intact at this point).
let us know how this turns out, good luck
"You can never be free until you let yourself go."