dell xps laptop, no audio

I was using laptop dell (xps l511Z, 64 bit, windows 10,) normally , just when i left for half an hour, the audio wasn't working. tried the fixes during troubleshooting, restarting etc, . audio icon has cross mark and "no speakers or headphones plugged in". before  it was showing "no audio output device is installed".
is it hardware  issue or driver problem?
also under device manager, "audio inputs and outputs " is missing. pls say step to step to resolve the issue.