clutch dosn't seem to work

[jakeouthwaite]

i recently replaced the engine in my corsa due to massive oil leeks. the new engine is exactly the same as the old one a 1.2 8 valve. the car can select all the gears while the engine inst running, but if i try it while the car is running when i press the clutch then select a gear it dosent seem to be disconecting properly. the clutch has plenty of meat on it so no problems there. im pretty shure i put the clutch back in the right way around but i dont want to have to either drop the engine or gearbox to find it is a simple fix.

[delta_kid]

gear selector maybe?