Go to Internet Explorer Settings and uncheck the disable debug options as shown below Add debugger; with terminator as first line in your javscript function. Once you have above steps done, clean all your browsing history and reload the form where you have this ribbon button. Open Debugger from F12 when debugger will open it will load CRM in browser again. Now when the javascript function is called, pointer will come at debugger to debug. Enjoy CRMing...!!