Question trying to add sound system to sharp tv as below but cannot get sound to work

Sep 12, 2021
I recently purchased the following for my daughter and her son is trying to add a sound system that we gave to them but no sound coming out. He has used a HDMI lead but still nothing. Can anyone advise regards settings etc please? The sound system has worked perfectly well on two of our tvs prior to this. Thank you

Sharp 50BJ2K 50" 4K Ultra HD Smart LED TV with Freeview HD, Ultra HD 4K HDR Display, Active Motion 400, Smart TV Aquos Net+ with apps including Netflix, HDMI 2.0 x 3 USB x 3, harman/kardon® sound / Dolby Digital/Digital+/ DTS 2.0/DTS HD, PVR - Record TV onto external USB or HDD, SD Card Slot