EGR problems pls help ?

i have a vauxall astra 1.6 envoy 2001
at first the Ecu Light was on so i took it for computer check and egr valve was the fault now i bought a new egr valve 4 £90 fixed it at the garage clear the codes on the computer 40min after the light is back on pls help me whats the problem who knows:?:?:?