car will not start

Hi guys, my mercedes vito 2012 started leaking coolant so we diagnosed it and found out it was the fuel filter housing that needed replacing. After replacing it, the leaking has stopped but the bus won't start now... the diagnostics do not show anything so we literally do not know what the issue...

I there i have a E270cdi 53 reg that will not even click when trying to start and glow plug light dose not come on and fan runs at full speed! battrey is fine 12.5 volts all fuses and relays are fine. im a mechanic and this car is just being a pain! can eny one help ?