toilet doesn't flush even after 2 plumber visits, to snake the sewer and also use a toilet auger
Here's a simple test:
Fill the bowl slowly until the water level reaches its maximum.
Once there take a small bucket, about the size of a ice cream pail, and quickly pour it into the bowl. This should start the siphonic action and make the toilet "flush".
If this works then the main jet is plugged and can sometimes be temporarily cleared by putting a small screwdriver into the jet and gently clearing it of build up.
If it does flush with the test and you can't clear the jet, a new bowl is required.
Cost would say complete toilet replacement.

Additionally, check to make sure the fill valves bowl primer tube is attached to the overflow tube so that the priming water is pouring into it and not into the tank itself.
If the bowl isn't being properly primed, a large portion of the flush action is being used to fill the bowl instead of inducing the syphonic action and clearing the bowl of waste and can cause the waste to become plugged in the goose neck (s-trap) or shortly after.