On Windows, sometimes a problem might occur with the Sound configuration and we will see this symbol in the taskbar: 

Let's go over the troubleshooting procedure:

1 - Make sure the auxiliary cable is plugged in all the way

This may seem silly, but if it's the problem then it's an easy fix. 

2 - Check Windows Sound settings

Sometimes sound devices are disabled by a user or by the system. To verify that output is enabled, open the 'Sound' menu one of three ways:

Run command:

Windows Search:

Taskbar:

Right-click the speaker icon in the taskbar:

3 - Try a power reset

Sometimes there are hardware malfunctions and the sound card on the machine might need a reset.  This more specifically applies to desktops.

Start by shutting the machine down, as we are going to unplug the machine and don't want it to lose power while being on.

After the machine has fully shut down, locate the power supply switch on the back of the machine.  Switch it to the off position:

If the machine does not have one, simply unplug the power cable and plug it back in.

4 - Time to call in the big guns

If the above did not work, it is most likely a hardware malfunction of the computer or administrative repairs need to be taken.  Please contact your IT department.