I haven’t used Audacity for a few months. When I tried yesterday my turntable wasn’t recognised. I have recently updated to El Capitan 10.11.1 – is this likely to be the issue? I am using Audacity 2.1.0.
Apple Care has looked at my iMac and say there is no problem with that and suggested I look at Audacity & my DAC hardware.
The first obvious possibility is having the two just miss each other. Audacity checks for new devices when it starts, so connect the turntable, let it settle and then start Audacity.
Use the Audacity Device Toolbar to switch to the turntable (if it’s listed).