[cotbu]

What type of pressure plate are you usiing? And how did you install the engine to transmission?

If you have a pressure plate with the fingers that wrap around the spring mechanism, they can get broken off when the input shaft slides up the pressure plate during an in car assembly. That small piece get lodged in back of the disc, which doesn't let the clutch disengage.

You can avoid this by taking you time and rotating the crank pulley while lower the engine into place, or mate the transmission and engine together on the ground then install.

This scenario requires removing the engine from the trans again to look at the pp and remove the broken pieces.

You should probably do this anyway even if it's not a broken pp finger. Could be a failed spring or whatever.