As said by Old Skool, fuel nozzle shimming can cause no start and/or delayed light off problems. However it won't cause the start relay to fail to latch. One of the most common causes for not latching, other than faulty relays, is the power lever angle rigging. If this is off by as little as .1 degree the FADEC will not see the throttle in the idle position. The rigging must be checked using the laptop computer. If this rigging is off the fly dedent rigging will probably be incorrect also.