Freelander td4 2001 won't start on the key

Have replaced the battery, replaced the terminals on battery, checked diesel pump, replaced filters, oil change, checked fuel on injectors. Cleaned all terminals on wiring Replaced starter and still nothing. However it starts like a dream with a push start. There is no white smoke on starting this way either. Drives like a dream with no tapping on the bottom end. Does anyone have any ideas pls???