Q. I want to compile the existing project and the compiler says it has problems with the ETHERNET command.

A. I can see the MC403 which does not work has 2.0268 which is relatively old.  The controller that does work has a different firmware version.

It is likely that the V2.0268 does not support all the ETHERNET function numbers so my suggestion is to load the same firmware as used in the working MC403.  Otherwise update to the latest 2.0322.