No soundbar on IPTV

Hello,

I have a little sound problem with my mother's IPTV. She can't get any sound. When she uses the directional button on the IPTV remote control, the sound bar that is supposed to appear on the right side of the screen doesn't show up. It's nothing. So we can't increase the volume. Do you know if it's a remote control issue? Or a setting? Thank you for your help.