Maybe go through the Realtek tools that is used to configure its outputs and inputs, and ensure that it is set with volume levels up near the top.
There is another thing I'll detail, in case it is involved. The Realtek system I have (and many are this way) is designed to allow you to re-assign certain output jacks to do different functions. But the way it works can cause your sound to disappear. So, with the Realtek system set as your Default Sound Playback device, follow this sequence.
1. Arrange your system so you can plug in and unplug speaker items from your back panel, and see your monitor screen and keyboard at the same time.
2. Unplug all the things on the back panel jacks for sound output, and any headphones plugged into the front jack. Now reboot your system so it realizes it has NO devices connected to output jacks.
3. Go into the Realtek system and set it for your speaker system - I will write as if you have a system like mine - 5.1 surround sound, plus headphones at the front panel.
4. Start with ONE speaker plug - say, the front left / right speakers. Plug that into its correct jack - usually green. Now check your monitor right away. It should pop up a little window saying that Realtek has detected something was plugged into that jack, and asking for what. It will suggest a default possibility, like the front left / right speakers. If you ignore that, the screen will disappear after a short time, and it will NOT use the suggestion it showed you. Instead, it will send out NOTHING on that jack! So, before the little window closes, answer it and tell it - even if only confirming its suggestion - exactly what you just plugged in.
5. On to the the next - say, the front middle / Subwoofer pair into the orange jack. Follow the same process - answer the little window.
6. Same again (if you have them) say, rear speaker pair into the grey jack, and answer the window.
7. Lastly, plug your headphones into the front and see if you need to answer for that new item, too.
Once this is complete, go to your Realtek configuration utility and use its test tools to output sounds to your speakers. Mine offers various moving sound patterns to check that all speakers are performing, and help you balance their volumes.
This process is necessary to get the mobo Realtek system to actually send sound out of its jacks. Maybe it will help your problem.