My 2001 buick park avenue security light is on. Is this the reason my car won't start?

Do you have the owner's manual there?

Yes

Does it help?

No Roy it doesn't help, try starting it and leave the key on for ten minutes, the security light will shut off and then you can turn the key off and try it again. You may have to do these steps three times. But usually that's only when you replace the ignition switch, it should be fine after the first try.

You don't have too be right on everything. You asked a question and I knew that the manual has 0 assistance with this issue so I answered your question so you know for future reference.