Using 3.5mm jack, don't know why sound stopped working. How do I turn back on?

Have you followed this troubleshooter?

https://support.xbox.com/en-IE/xbox-one/accessories/wired-headset-help

If it's a wired headset and out of the 90 day warranty period I would try replacing the 3.5mm headphone jack. We've had 3 controllers stop working with a wired headset. (all other buttons, etc. still worked) I replaced the 3.5mm jack and now have sound
and mic thru the wired headset! You can find the part on Amazon for around $5.00 USD. Easy fix.

YouTube on how to replace - https://www.youtube.com/watch?v=FJ7Q-KREs0w

All game sounds and chat functionality work fantastic with the new controller with the 3.5mm jack. I am currently using a pair of stereo Gioteck HC2's plugged into the 3.5mm jack and they work great. Any gaming headset that is wired should also work fine
through it.

You can use the Optical Out to an optical In device - but I do not think the Sound Blaster device is an Input device. Do you have a model number on the sound blaster item, I could not find anything on creative box.

You can use a 3.5mm jack to the sound blaster it should have a Green slot for audio in, the output for the 3.5mm jack should be on the back of the monitor.

Or you could get a set of headphones with optical input Turtle beach etc..

Also Here is how to use optical input on the sound blaster device.

support.creative.com/.../ShowArticle.aspx

I dont have a remote with 3.5mm jack. Why do I have to leave one USB open if I want to use the 3.5mm jack?

Is there any usb-microphone that is compatible with Xbox One?