Too little information there is many things effecting who you can set as certain councillors. For example hindus can only appoint characters with kshatriya trait to be the marshal. Gurus also can't be selected as marshals.
This may very well be the issue. I am Hindu as are most in my realm, and I did not know about this Hindu trait requirement. I'll check that out. thanks (edit: Yep, pretty sure that was it. Guy is was trying to find was not Kshatriya)