without going through all answers [sleep time] think you said you 'hadn't' had the clutch apart but had--had the cover off only. Working on the theory that i misunderstood i'll imagine you had the clutch pressure plate off [end plate] & put it on wrong--think you get 3 shots of getting it right but has 5 springs, so if it's wrong it sits against end of splines instead of 'on' them, consequently it wont drive [engage] as plates not compressed. Sorry if i got the wrong end of the stick--just a hunch. If you realy didn't touch anything except have cover off & back on then--i give up, for now anyway. Good luck.