WoA - Fodder Machine

Hello fellow farmers, I am very confused at the moment 😅 I just unlocked the barn and the "fodder machine" within. Judy and the tutorial told me to put weeds in it to make fodder. In the past I collected some weeds from the field between the first two towns so I tried to put them into the machine. But it does not work. I choose "make fodder" and for weeds it says "0/18" and I cannot make anything. Am I doing something wrong? Any help would be welcomed as my chicken is hungry now 😵, thank you very much :)