fishfanglv are you dragging the addon file into construct program when it is open? You should get a pop up asking you if you wish to install it.
I just tried it and it was fine. I will need to know your Construct version number if you are still having issues.
Thanks, it works. At first I copied it into plugin folder.
P.S. Maybe you should add in Q&A how to import it into C2, like "Drag addon into Construct 2 when it's running, and then install".