The system sound is not working... solved

[Husse]

Make sure that you have not changed anything in Mint
It is not as strange as it seems (maybe stranger ) because some software (Windows to name one) can do changes to the firmware
But I doubt Ubuntu (which gOS is based on like Mint) has a different capacity to do this
There is one thing - some old(er) notebooks must have the modem enabled to get sound - worth checking
And start gOS, check sound, shut down and let rest for 10 minutes or so and boot Mint again

[Husse]

To help you beyond this I need to know your hardware and exactly which version of Mint you use
Hardware - run lspci in a terminal