1.What is the make and model of the computer?
2• Did you try connecting different HDMI port and check if it works?
3• Which application are you using to stream movies on the computer?
HDMI cables do support audio signals, but not all HDMI-enabled video cards support audio. If your HDTV has an audio input, you might be able to connect a separate audio cable from your computer's sound card directly to the TV. Otherwise, you'll need to connect the audio signal to a different output device, such as external computer speakers or your home stereo system. Follow these methods and check if it helps: