merc C250 not seeing key and won't turn in ignition??

merc C250 on an R reg it has been sat for 9 months i've recharged the battery and put new batterys in key but can not unlock it by remote have to use the little key slid in the remote then once in the car the alarm keeps going which i can't turn off and it won't let me turn the ignition on?? seems like it not seeing the key?? i'm stuck now can anyone help. Also this car has had alot of money spent on it due to diesel keep running back resulting in starting problems. someone has suggested there is a pipe running down O/S of the car that has been known to cause this fault has anyone heard this befor