You need your player blueprint to be based on the Character class in order to use the CharacterMovement component (the character blueprints for most of the example projects such as ThirdPerson, FirstPerson, TopDown etc. uses this).
I used the TopDown example as test and I was able to do this by adding this into the TowDownCharacter BP:
Make you have “Use Controller Desired Rotation” enabled in the CharacterMovement component.
Then make you set the camera to be facing directly down (-90 degrees on the Y axis of the spring arm) or else you will probably have to do a trace instead of using FindLookAtRotation.
Also I deleted all the stuff from the TowDownController BP, you only need to enable the mouse cursor in there.
Let me know if you have any problems!