Maintenance light does not go off despite resetting

After taking the vehicle to the service center and having it serviced, the maintenance light started coming on again. Also, the engine malfunction light is on. At the service center, they said it was caused by the fuel tank. Can someone with knowledge give me some advice about these people, please?

Hello, sir. What engine do you have in your car? 1.6 VTI, 1.4, etc. Since there are multiple engines, you need to interpret them accordingly. Have you used a diagnostic tool to determine the source of the fault light?