Need some more info here, what are you trying to play from the USB? Did you look in the manual for the TV if it can read a USB stick and what format the file system needs to be and what format files it can play? Do you mean when you play a movie stored on USB you get picture but no sound? Could be due to the external speaker setup, you may need to change the audio options to enable PCM. https://www.techwalla.com/articles/how-to-change-my-tv-to-pcm
Assuming that you have the drive plugged directly into the TV and you are getting sound on the TV speakers it may be that the TV just won't output audio from the USB drive.
If you don't get sound on the TV speakers then you may need to check the audio on the files. Might not be compatible with the TV.