3 things are possible
- The character you want to cast to isnt named Run_Characcter but rather RunCharacter or nruCharacter or something
- Your trying to cast in a class that it wont work in like i dunno some weid class
- Turn off context sensitive you miht be dragging off a pin, alternatively right click in blank space and search “cast char” and look for it, change char to run or just search “cast” for all options. It will be the name of your characters bluerint class though.