Dell product not showing up, SupportAssist not working (trying to fix headset issue)

So I'm having a host of problems with my product. I'm not sure exactly what model I have and every time I search the service tag ( ) it can't find my laptop. I've been trying to do this to get some support because I got a new headset after what I thought was the mic from my last one stopped working but the mic from this one also isn't working on this computer, but worked just fine on other ones. I found info that opening Realtek audio manager would let me get it to work, but the executable I have downloaded just won't open. I found some MORE tutorials saying to figure out the motherboard's company to download the Realtek driver version that's said to work with your specific motherboard but that info isn't listed anywhere on this computer and so I thought to go to Dell since it's a Dell product, but no matter what I can't find my laptop anywhere, not even in my products. I'm thinking that maybe the fact that this is a "Refurbished" version that I got from Dell after they didn't have the parts to repair my last Dell laptop of either the same or a similar model, it assumes it's not an official Dell product. I'm just frustrated because I spent good money on this headset and this computer only for it to have countless issues.