No hay sonido cable óptico

Good day

If there's an expert on this or someone who's been through a similar situation and could guide me...

I just finished my home theater setup, haha

It's a Dess c5 Pro projector

I have a Fire TV Stick connected via HDMI

And a Billboard Studio Pro 2.1 soundbar connected via optical cable. I have everything connected, and there's a red light at the other end. In the projector's interface, I changed the audio output to optical (SPDIF), but there's no sound. I looked for more audio settings, but there aren't any. I connected the soundbar to the Fire TV via Bluetooth, and it works, but the audio buffers terribly because of my internet connection. Any experts on this, please?