Can put gas in the tank.

I took the car into the mechanic shop for a simple gas leak. They replaced two valves in the gas tank and now the check engine light came on (gas tank pressure sensor) and I can't put gas in it. I have taken it back 3 times now and every time they say they replace the same two valves and clear the check engine light. Then I drive it for a week put gas in it twice, then I have the same issue. Check engine light comes on and I can't put gas into the tank because of the pressure, gas spills out onto the ground. What is wrong with my car?