Have you set up a "my Presonus account and registered all your products? If so, then go to your "My Presonus" account and make sure you download and install the latest drivers for your product, and the same goes for Studio one, and any controllers or other features you want to use, like Ipad remote. ALWAYS be on the latest versions for the best experience.
Now, stat a tech ticket so your in line and if we get you sorted here you can always cancel it...
There are routing options you need to be aware of, and if your routing audio back from the digital inputs you need to route them
https://pae-web.presonusmusic.com/downloads/products/pdf/StudioLiveSeriesIII_OwnersManual_14022017.pdf
Section 8.1.4
You also need to know and route the audio to the output you want it to go to. With these mixers your going to need to become familiar with the manual, and the features and operation of the board!
Best regards