2008 mustang wont start

Do the lights come on? Check the battery for power. Unless its completely dead you should get some noise from the starter. If you have power and it makes ZERO noise when you try to crank, it may be a clutch/neutral safety switch. You did not specify if the car was auto/manual but it fundamentally operates the same as far as the switch is concerned. If the clutch is pressed it will activate a switch on the pedal assembly telling the car it's okay to start. With automatics its usually connected to the gear selector in the center console letting the car know if it's in park or neutral in order to start. If the switch fails, the car doesnt know what gear it's in and prevents you from starting the car.

Just to add, part of your security system is starter motor disable. Something to check. good luck

or its the chip in your key.