Question

My mixer is receiving sound from the daw but no sound is coming out of the monitors. It was working fine before.

Answer 1

Read the following and ensure you have your DAW setup correctly.

https://support.presonus.com/hc/en-us/articles/115001134163-Tape-In-USB-Playback-Routing-on-the-StudioLive-Series-III

Answer 2

I just bought one and had the same exact thing happen..

https://pae-web.presonusmusic.com/downloads/products/pdf/Studio_One_Integration_and_Quick_Start_for_StudioLive_Mixers_Reference_Manual_V2-EN_25032019.pdf

Page 11:

If you would like to mix inside Studio One, you will need to create at least one stereo output for the Main bus. In general, it is recommended that you use the Tape Left/ Right Return for Series III mixers as this allows you to return audio to your mixer without using a channel on your StudioLive. By default, USB Returns 63-64 are the source for the Tape input. This can be changed in the Input Source menu as well.

You have to setup a Tape input channel in console mode.. add that buss as an output in studio one.. then route your main to that console buss.. 

ALSO under Tape "EDIT " blue button right side by touch screen on the console.. Increase the "Tape to Main" Volume since by default its turned all the way down.. thus no sound even if setup right.  That was the main problem I had..