Hello, I hope the following assists you.
If the EGR valve is replaced on this engine then the EGR learned values need to be reset to account for the new valve, not doing this can cause the engine management light to come on.
Ideally you need to get the fault codes from the engine management control module memory to confirm that it is still an EGR concern putting the light on, it is possible that there is another problem causing the light to come on. If the garage retrieve the codes and there is still an EGR fault after the values have been reset (not just resetting the light) then this would suggest a fault with the EGR valve wiring. As the light keeps coming on the engine management is detecting a fault, turning the light off isn't resolving the fault it just clears the memory until the fault is detected again.
I hope this helps but if you have more questions regarding this let me know and I'll reply as soon as I'm able to.