Can't change all my farm plots to advance class

[Jaymacibe]

I been looking online and I can't find an answer to this yet.

I have a few farm plots. I recently unlocked the advance farm class. I was able to change out only 2/5 of my plots to advance class.
I checked all the others and they only can be basic. All of them are max level.

I looked through King's guide playlist, didn't notice my answer, I went through the wiki, can't find my answer.

Why only 2 out of my 5 farm plots allow to be advance class?

 

[Eichkater]

The assigned farmer needs to have at least 5 Endurance to build and use it. You can turn that off though in the CP desk if you want.