Do you have any binding, and are you sure everything is installed and lined up properly ?
I would disassemble the entire clutch system and inspect every part for it's functionability.
With any moving parts, something can be off a tad bit, or very small can be broken and it won't work right or not at all. Look at the disk's springs and fingers. Move the bearing back and forth on the shaft.
If that doesn't work, give it a hard swift kick !
