When you first log in you will have to grant Sales Sling permission to use your microphone and send you notifications.  

Note:  This may have to be done periodically down the road as well, if you change or refresh certain Chrome settings.  Refer back to these steps if your microphone is ever not working.  

1.  You should be prompted to allow access to both microphone and notifications when you first enter Sales Sling.  Make sure to select allow in both boxes that pop up: 

2.  If you are not prompted with the above box for some reason, you may manually turn on these permissions by clicking on the Green Padlock that says Secure next to the website address.