Can't assign motion in mecanim

I am using a model with animations I imported from Blender. I may have done this wrong but I don’t think so. I am using mecanim (or trying to) but when I create a new state and try to drag an animation on the motion slot it won’t go there, it just stays blank.

Having the same issue! Had it once before but can’t remember how I solved it. My guess is restarting Unity