Are you editing an alread modded file?
Original files should work with EEA 9.0, but 99,5% of already modded files do not, because by the time they were modded, EEA 9.0 did not exist as 9.0 is slightly different, it is not compatible.
So as we usually say: Games pre F1 22 use EEA pre 9.0 (8.1 at best)