Why can't I press the Add component button?

I attached the image below.
Please tell me if you can’t judge with this image alone.
Thank you in advance.

284767-screenshot-20190804-142242.png

Hello Yuuki Mumei,
You will need to stop your game/simulation before you can make any changes to the code, you can’t edit blueprints while the game is running.

Thank you so much for your help…