Changing Materials Button does not click

Hi guys! Please help me I can’t do it anymore. I have tried to change materials in my project in three different ways following youtube videos because I have to do this foi my architecture school project and all of them failed and I don’t know why. I will be sending some photos of my blueprints, but my problem is that when I click on the material button that is supposed to make the change on the material of the floor, nothing happens, it does not even click. You can see in the last image, the OK button clicks normal but the three squares with the materials do not click and/or change the material. Thank you so much for anyone who might be able to help me I’m desperate.
I followed this tutorial in all the steps: Unreal Engine: Change Material in Blueprints - YouTube