To help you get your phone back up and running, please let me know: What is the of your phone? Which Android version or stock ROM are you trying to flash?
Fixing the CMDongle error is useless if your computer cannot communicate with your phone. You must ensure your Qualcomm drivers are correctly installed. Download the drivers. Install them on your Windows PC. To test the connection: Power off your phone completely. Hold Volume Up + Volume Down simultaneously. To help you get your phone back up
Connect the phone to the PC via USB while holding the buttons. To help you get your phone back up