Black texture when i try to make a material

Hello. I’m using Unreal 4.14.3 and i have a question. Why does my texture look black when i try to do a material with it? I need to wait about 10 minutes to load and if i want to make some changes (make a simple node) it turns back to black and i have to wait 10 minutes to load again. Texture is 1024 x 1024 and i tried with 512 x 512 and it nothing changes. Help (sorry for bad english)