I have a lennox elite series model 10GCS036-100-1PA , it worked great yesterday but nothing at all today, I checked the circuit bracker and it is fine , can you tell me what the problem might be please , I can't afford to have anyone come look at it right now and am burning up here in this heat

It's almost impossible to tell you what is wrong with your unit over the internet. You need to bite the bullet and call out an a/c tech and have them test the components to see which one failed If it ran okay until today then it's probably something simple like a failed relay switch which is not that big a deal to replace. Would not recommend you try to repair this yourself if you know zip about an a/c unit. You could do more damage to the unit AND yourself with a do it yourself repair. Also, if you have the money for a Lennox (which is one of the highest end a/c's there is) am really surprised you don't have any money for a repair person. Is this unit still under warranty? If if is then call Lennox to fix it.

When set to cool, does the inside blower work?
Check Breakers and disconnects.
No response from thermostat could be bad transformer/fuse. Newer thermostats have batteries that go bad?