1. The sound is turned off or muted: Please check your computer sound settings to ensure that the volume is not turned off or muted. You can view and adjust volume settings by clicking the volume icon in the lower right corner of the taskbar.

2. The sound device settings are incorrect: Please check whether the sound device settings of your computer are correct. You can select "Preferences" under the "Options" menu in GOM Player and select the correct audio device in the "Audio" tab.

3. The file itself has no background music: Please check whether your file itself has no background music. You can try opening the file with another multimedia player and check if there is background music.

4. Lack of audio decoder: If your computer lacks the relevant audio decoder, GOM Player may not be able to play background music normally. You can try downloading and installing audio and video codec packages such as K-Lite Codec Pack to support more audio formats.