Ok. Maybe run through some troubleshooting. You have probably tried this already, but it doesn't hurt to write it out point by point.
Firstly, is the QU set up correctly? I don't have that mixer (I use the X32), but you usually have to route the desk input channels to the correct USB output channels with Allen & Heath mixers. There's details of this on page 78 of the manual available here:https://www.allen-heath.com/media/Qu-Mi ... 372_10.pdf
Once that's done we can look at logic. Hook up the USB to the mac and click on the speaker icon in the top right of the screen (volume and audio control). Does the QU pop up there as an option? If not, it's not connecting to the mac correctly, so either the desk is faulty, or your USB cable is faulty, or your USB port on the Mac is broken.
If you can see the QU on that menu then you can load up logic.
Once logic is open go: Logic Pro X > Preferences > Audio
Here you can select the QU as your input/output device.
Once you've done that you can create a new project and create a new audio track. Make sure the correct input is selected, then hit the red R button at the bottom of the channel fader. Level should appear.
It should be that simple, as Allen & Heath stuff is class compliant, so shouldn't need audio drivers or anything else on a Mac. If it still doesn't work then there's something really wrong somewhere, so you'll probably need to find someone who can help. Luckily you've bought a QU now. Allen & Heath, in my experience, are brilliant on their customer service, so I'd try giving them a call.