Sprinter 311 slipping clutch, still?

2003 311 merc sprinter. Clutch started to slip. So I fitted a new full clutch but with solid flywheel.
The clutch That came out did not show signs of wear apart from the dual mass flywheel with slight wear.
Clutch still slips. Replaced master cylinder (with a second hand one) clutch still slips.
The clutch pedal is very, very light.
Do I need merc fluid?
Have I bought a duff clutch?
I did not use the "tool" to compress the springs when installing the new clutch.
Has anybody got a clue?