What would be the major problem for car from starting when it ran befor problem

Did the dash lights illuminate (ie: ABS light, check engine light, oil light, etc) when the key was turned to the "on" position? If not, probably a battery or connection issue. If on, then when key turned to "start" position did the starter engage (make the engine turn over), do nothing, or did you only hear a 'click' sound? If the engine turned, probably a fuel or ignition prob. If not, may still be a battery or connection issue. Check battery terminals for tightness/corrosion & clean/tighten as needed. If no change, and you think it's a battery issue, prob a poor ground connection (engine-frame or battery-frame). After that, may be starter, switch or wiring issues.