CK II - Heir designation with civilized reformation option not working

[Meme_Thief_]

One line summary of your issue
Heir designation with civilized reformation option not working

Game Version
3.0

What expansions do you have installed?
Jade Dragon,
Monks & Mystics,
The Reapers Due,
Conclave,
Horse Lords,
Way of Life,
Charlemagne,
Rajas of India,
Sons of Abraham,
The Old Gods,
The Republic,
Legacy of Rome,
Sword of Islam,
Holy Fury, All of the above

Do you have mods enabled?
No

Please explain your issue is in as much detail as possible.
Whenever I try to designate one of my sons as heir or once I press on the designate heir button above their heads the button will disappear and my first son will stay heir and the chosen one will not

Steps to reproduce the issue.
reform hellenic religion and choose the civilized reformation option. than attempt to designate one of your sons

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[mattrhearn]

Heir designation isn't compatible with gavelkind or elective succession types. Since, as the Roman/Byzantine Empire, you are locked into Imperial Elective, you can't use the Meritocracy aspect of Civilized.

If, however, you lost the Empire title on succession and became a feudal supercount with viceroyalties as higher titles (or landed if you can swing it), it would become useful to you.

 

[Meme_Thief_]

Heir designation isn't compatible with gavelkind or elective succession types. Since, as the Roman/Byzantine Empire, you are locked into Imperial Elective, you can't use the Meritocracy aspect of Civilized.

If, however, you lost the Empire title on succession and became a feudal supercount with viceroyalties as higher titles (or landed if you can swing it), it would become useful to you.

I just noticed this but thank you anyways