u/Better-Hovercraft150

I was playing a random mobile root game recently just to mess around with it and see what it’s like playing online when I ran into what I think is a bug but could also be me not understanding the rules of the game
I’ve posted a screenshot. Why can’t I turn the warrior of mine in the bottom right clearing into a sympathy. The game wouldn’t let me multiple turns in a row and I lost the win to cats because of that later on. To my knowledge the only restriction for replacing a warrior for a sympathy is that there isn’t a sympathy already in the clearing but the game just wouldn’t let me put a sympathy in that clearing. Could it have to do with the keep? I’m not sure someone please let me know what I’m missing.