Why your Toyota Camry wont start?

Could be a myriad of causes. If your light is on- check codes and that will help pinpint. If it doesn't crank could be the starter or power to. If it does, and PATS (security) not activated, it needs 3 things to run, compression, air/fuel, spark. Has gas, check fuel pressure at rail, that ok, check spark, that ok, check compression.