How to Stop Your Dog From Barking at Everything

The mailman. The neighbor's car door. A leaf. Something on the television that you genuinely cannot identify. 

You have tried "quiet." You have tried ignoring it. You have tried the treat thing where you are supposed to reward the silence, except there is never any silence to reward. 

And somewhere in the last few months, you stopped inviting people over. 

Here is the part that changes this: your dog is not barking for one reason. He is barking for several, and they need completely different fixes. That is why the advice you found online did not work. It was probably solving a different problem than the one you have.