If you installed them all from your PCS download page, that's not how you configure Windows 10. I'd strongly advise getting advice on how to properly clean install and configure windows as if not done properly you'll have various issues.
I don't think you're eligible for any refund as the...
Amazon seem to have a few in various colours, the full set is here, but they do individual cables too:
The case port uses the same soundcard, but motherboards don't support the newer 3 pole 2.5" jacks that you find on lower end headsets and mobile headsets where it includes a microphone. That why you need to use the splitter for the mothrerboard ports to split it down to basic 2 channel.
Again, they wouldn't work out the back without a splitter, so we can't use those to troubleshoot.
You can see the audio is definitely playing out of the realtek channel.
I guess it's possible that it's a failed port on the motherboard, but I've literally never ever heard of that happening...
Ok, you need to just answer the questions directly if possible.
What port do you have the speaker plugged into? Have you turned up the volume on the speakers and made sure the volume is up on the PC?
Do you have a normal standard pair of headphones to test with?