Some question about SelectTool of .glyphsTool plug-in

I made a SelectTool of .glyphsTool plug-in. One glyphs can be displayed on the toolbar when it is installed, and it can be used. The other glyphs software has no response after it is installed. I tested def start (self), and it didn’t execute. Why is ?

Which error message do you get in the Console?
Where is your plug-in? Did you put it in a GitHub repository?