Oil was low check guages light came on and now won't start. What is the problem?

Assuming you added oil, there are a multitude if things that will prevent a car from starting, far too many to list here. Yeah, I know, no help. But simply asking what is the problem is not enough information. Start with the basics, stick a screwdriver in a spark plug wire, ground it on the plug, see if you have spark. Blue. Yellow is weak. To boil it down, spark, fuel, timing.

did it shut off while running, or did you power down the engine? (as in seized it from no oil)....how low was the dip-stick? help David and I a bit more with this one please...does it crank and not start, or seem dead, with no response......

Oil was added, it turns over, there is spark but it won't start. It shut off while it was running. He added 3 litres of oil.

Alot of reasons , if the car was run along time with little oil the engine could have seized ...