Dragoo , can your player still be reconisged by the MP3 Utilities Upgrade Tool? If so, try to extract your player's firmware, repair it and then re-flashing it back. See if it solves the problem.
If not, you will need to go to the downloads section and try random firmwares that matches your player specifications (or as close as possible)
Here.
If your player cannot be reconisged anymore, you will need to follow the Dead Player Recovery Guide
Here.