An anti theft system can prevent spark, a defective engine sensor such as a camshaft position sensor or crankshaft position sensor can contribute to lack of ignition spark. Wiring harness issues, fuses, bad electrical connections, relays or Electronic Control Unit problems can all effect spark. Could be a bad ignition switch or something as simple as poor battery connections in short its difficult without being able to drive your car and experience the problem, and do some basic diagnostic tests first hand it is difficult to speculate as to the cause.