Here is your fix for the no sound issue in Sims 4.
Close the game then Go to Your "Documents", Then Go to "Electronic Arts", Then Go to "The Sims 4", Then go to "Options" and delete the file, Next go to "config" and delete that, Lastly load up Sims 4 and your volume will work. If it cuts out them go on to the next fix below. My Dad said your welcome keep gaming and play on.
Here's another fix that can work if the Config and options file reapears in the documents folder and sound cuts out again even though you have current sound drivers. I'm the Dad. Play on players
First Hover your mouse to the right corner of the bottom of the screen on that tiny speaker icon, then press right click and open playback devices and then scroll to the speakers with a green sigh on it icon. Then select advanced and be sure that the two options are selected: allow application to take control of this device and give exclusive mode applications priority. Now the last step is to lower or raise the Bits and Hz sound quality frequencies and click apply then try and start the game. Up (test) or down (test) freq adjustment until the sound stays on. This should fix it. My dad made a tuorial for this online but EA wont allow me to link to it. This should be your fix since you have sound at the flash screen then it cuts off. Remember lower the frequencey or raise it until the sound stays. He raised my frequency to 24Bit 48,000hz and my sound stayed on from the start till finish everyday since.