Hi and thanks for any help all ideas are welcome

I have a 3l diesel m57 engine, was running spot on but had a oil leak from the valve cover so I changed the gasket, and put it back together but now it won't start, I have the manifold off
there is 40l of diesel in it, all the injectors have diesel flowing and no air lock, I tried easy start and still it will not fire just cranks over, iv tried to let it prime for 10mins by turning it on and off, the battery is full changed,

Don't know what to do from here any ideas are welcome and thx