Why can't I start a great holy war

I am the Fylkir (reformed norse version of the pope) and would very much like to know why I cannot start another holy war.

I am playing as Empire of Britannia. I have all the holy sites. The year is over 1100 and both the Muslims and the Catholics have called crusades before. The norse faith has over 100% moral authority. I have even started (and won) 4 great holy wars earlier, last one being about 30 years ago.

Why can't I start a holy war now?

I would double check the time since the last Great Holy War ended. I believe the cooldown for the Great Holy War CB is 30 years from the end of your last Great Holy War.