Espresso does not make

Does the water stop while the pump is still operating ? Is the "READY" light ON when the water stops ? You need to be more specific about exactly what the symptoms are because these machines are fairly complex and have pressure and temperature sensors to make sure the shots are consistently good. You should make sure to flush your machine regularly with descaler because scale buildup is the most common problem that you'll run into with coffee machines. You can get descaler at any decent hardware store or you can also use "CLR" which works just as well. If the pump keeps running and the water flow just stops, then I would suspect that there is a clogged line or the grind is too fine. Try pouring a shot without using the spoon to see if the water flows freely. If it flows OK, then your grind is probably the problem. If it still does not flow freely, descale the machine several times and see if that makes things better. If you've never descaled your machine, then use a strong descaler or CLR concentration and run the descaling liquid through the machine several times, or even let the descaler sit and soak the inner workings overnight, If the just pump stops prematurely during a shot, then there is probably a sensor problem with the machine. Take it in to a repair place for diagnosis. If you can't find a place that repairs espresso machines, ask the manager of your local Starbucks what repair company they use, since Starbucks stores have contracts with people to routinely service and repair their own equipment.

Remove the portafilter and press the brew button, if the water flows from the head with a nice flow then the problem is with the grind (too fine), or the coffee has been Tamp too hard.
If water barely flows when you press the button then try backwashing the machine and removing the shower screen to clean it.