Can't nominate Duke for elective Kingdom

[Loderingo]

I am K of Burgundy with elective. I wished to nominate my grandson as heir so I made him Duke of Burgundy. I still can't nominate him though. I can nominate other Dukes in the de jure Kingdom of Burgundy and also Dukes not in the de jure Kingdom. He is not heir to a bishopric.

Any ideas why not or is it a bug?

 

[unmerged(51332)]

What are his personal stats? If they're pathetically low it might undermine his status despite his dukedom.

 

[Veldmaarschalk]

Wrong forum