New unit added with Mobh. OOB Editor won't appear

[Horses]

Dear,

I have just added a new unit to a german OOB (Coastal Fort with big Naval gun) in an unused unit slot with the mobhack oob editor but this new unit does not appear if I generate a battle or have a look into the Enzyklopedia.

On the other hand if I change the unit data of e.g. a coastal fort (e.g. other gun)the change will be accepted.

Any hint what I'm making wrong ?

Thanks and Regards