can't debug web app in flashbuilder

          I want to debug a web application in flashBuilder4.6 , But it prompts "The Flash Builder debugger can not connect to a running application". I'm using firefox 53.0.3(32),Because only it can use flashPlayer for debugger.     Very helpless, now flashbuilder can not connect to the firefox application.

          Do not know if you can give me some advice, then I will be very happy, and thank you！