Can't Use Furnaces

I was playing a fresh world in survival and after crafting a furnace, I tried to make some charcoal. I placed the log in and after trying to put the fuel in, it didn't switch to the fuel box. I tried to take the log back out and couldn't. The only thing that I was able to do in it was close the GUI. I tried going out and back in the world AND restarting my Minecraft Pocket Edition and it didn't work.