I have a Lennox heating

I have a Lennox heating system,
last night I came home and my house was cold but I could hear the system running.
I went up in the attic and noticed that there was no flames. So I turned everything off for about 5 minutes and then tried to fire up the automatic polite light.
It will not fire up at all, the big fan motor will run but that’s it.
It’s like the system has no gas to light it up. I tried to do this for about an hour. I even took a lighter to see if there was gas.