Ideapad 100-15IBY Why my speaker doesn't work?

@yosephmesert try some headphone and see if those work. It is possible that your headphone jack is stuck and thinks there are headphones plugged in. A few puffs of air and inserting and removal of the headphone jack in quick succession may free a stuck connector.

Of course there is always the possibility of a bad speaker or even bad audio IC on your motherboard. This assumes that you have checked your settings in your OS to make sure it is turned on and the volume is turned up.

Here is the Lenovo Ideapad 100 15IBY Hardware Maintenance Manual and page 50 shows you how to work on the speakers. My prime suspect is the head phone jack.... ;-)